English

• 1.   Introduction

  Great advancement has been made in transition metal catalyzed C-H bond activation and functionalization in the past 20 years [1-4]. The merits of direct C-H bond functionalization could reach its full extension only when site selective is achieved because there are almost always multiple C-H bonds in any organic substrate. The most common and successful strategy to address this selective challenge is using substrates containing coordinating ligands, namely directing groups [5, 6]. By coordinate to transition metal, the directing group could deliver the catalytic center to a proximal C-H bond and therefore force the C-H bondactivating event to occur in a controlled manner. A plenty of directing groups have been devised for this purpose, and due to its vast structural diversity, the N-containing directing groups constitute the major and most important part. These N-containing directing groups span from various aromatic N-heterocycles, amines, amides, imides and imines to hydrazones, oximes, triazoles, and ureas, etc.[7-40].

  Polycyclic aromatic compounds have been found increasing applications in functional materials in virtue of their excellent electro-and photo-chemical properties [41-45], which very often could be modulated through the introduction of multiple substituents on the arene core [46-49]. Metal catalyzed coupling of arene with two fold internal alkynes provides an efficient arene homologation method for poly-substituted polycyclic aromatic compounds [50-61]. Direct site selective homologation of unpreactivated arenes, which involves double C-H activation is highly appreciated as this method can provide polycyclic aromatic compounds in both efficient and controlled manner from easily accessible un-functionalized arenes [62-65]. Here, we would like to report a urea group directed arene homologation catalyzed by Rh (Ⅲ) complex employing either symmetric or unsymmetrical internal alkynes as coupling partners.

  2.   Experimental

  2.1   General

  ¹H NMR and ¹³C NMR spectra were recorded using Bruker AV-300/AV-400/AV-500 spectrometers. Analytical thin layer chromatography was performed on 0.25 μm extra hard silica gel plates with UV254 fluorescent indicator and/or by exposure to phosphomolybdic acid followed by brief heating with a heat gun. Liquid chromatography (flash chromatography) was performed on 60 Å (40-60 μm) mesh silica gel (SiO₂). All reactions were carried out under nitrogen or argon with anhydrous solvents in flame-dried glassware, unless otherwise noted. All reagents were commercially obtained and, where appropriate, purified prior to use.

  2.2   General procedure for the homologation of aryl ureas

  A mixture of the diphenylacetylene 2 (1.0 mmol, 2.5 eq.), 1 (0.4 mmol), [Cp^*RhCl₂]₂ (6.2 mg, 0.01 mmol, 2.5 mol%), Cu (OAc)₂ (188 mg, 1 mmol, 2.5 eq.), and AgSbF₆ (28 mg, 0.08 mmol, 20.0 mmol%) were weighted into a Schlenk tube equipped with a stir bar. t-AmOH (2 mL) was added and the mixture was stirred at 120 ℃ for 24 h under N₂ atmosphere. The reaction mixture was extracted with DCM for three times, and the combined organic layers were then dried over anhydrous Na₂SO₄, filtered, and the solvent was removed under reduced pressure. The crude product was purified by column chromatography on silica gel, eluted by hexane/EtOAc=3:1 then 2:1 to afford the desired product 3.

  Characterization and spectra for new compounds are compiled in Supporting information.

  3.   Results and discussion

  Our study commenced with urea 1a and diphenyl acetylene 2a (Table 1). Using an effective protocol disclosed by Fagnou team, several popular transition metal catalysts for oxidative C-H functionalization were explored. Pd (OAc)₂ and [RuCl₂(P-Cymene)]₂ failed to promote any reaction (entries 1-3). (Cp^*RhCl₂)₂ activated by AgSbF₆ did catalyze the desired arene homologation reaction and t-AmOH is the solvent of choice for good yield (entries 4 and 5). It was also found that Cu (OAc)₂ was a necessary oxidant and AgSbF₆ was a critical additive for this reaction to proceed smoothly (entries 5-7).

  表 1

  

  表 1  Condition optimization for oxidative condensation of phenyl urea with alkyne.^a

  Table 1.  Condition optimization for oxidative condensation of phenyl urea with alkyne.^a

  下载: 导出CSV

  With the optimal conditions in hand, an array of urea substrates 1 were submitted to the reaction with diphenyl acetylene 2a (Table 2). Meta substituted ureas, such as 1b and 1c were feasible substrates to give 5, 6, 7, 8-tetraphenyl naphthalene 3ba and 3ca in yields of more than 60% (entries 2-3). On the other hand, ortho- and para- substituents decreased the yield dramatically, as both tetraphenyl naphthalenes 3 da and 3ea were obtain from 1d to 1e in less than 20% yields (entries 4-5). N, N-Diphenyl urea 1f condensed with diphenyl acetylene to give rise to 3fa in 27% yield (entry 6). These outcomes may be the results of collective steric effects of both aryl substituents and bulky Cp^* ligand on metal center, which will be discussed later on.

  表 2

  

  表 2  Arene homologation of aryl ureas with dipenyl acetylene.^a

  Table 2.  Arene homologation of aryl ureas with dipenyl acetylene.^a

  下载: 导出CSV

  Further studies using unsymmetrical alkynes as the homologation partners highlight the virtue of this protocol (Table 3). Condensation of phenyl methyl acetylene 2b with urea 1a, 1b, 1c gave related 5, 8-dimethyl-6, 7-diphenyl naphthalenes 3ab, 3bb, 3cb in 60%-70% yields. The structure of 3ab was established by extensive NMR experiments including, 2D ¹H-¹H Noesy experiments. The selectivity demonstrated by these reactions is amazing as only one single regioisomer is produced out of four possible isomers. Moreover, to our delight, ortho substituted phenyl urea 1e achieved a much higher yield for 5, 8-dimethyl-6, 7-diphenyl naphthale 3eb (Table 3, entry 4, 63%) than the yield for 5, 6, 7, 8-tetraphenyl naphthalene 3ea (Table 2, entry 5, 18%). Methoxymethyl phenyl acetylene 2c is also condensed with 1a to give 3ac in 51% yield with exclusive regioselectivity, while alkynes 2d and 2e are not feasible coupling partners for this reaction.

  表 3

  

  表 3  Arene homologation of aryl ureas with unsymmetrical acetylenes.^a

  Table 3.  Arene homologation of aryl ureas with unsymmetrical acetylenes.^a

  下载: 导出CSV

  Based on previous studies [11, 66-70] and the data collected in this research, a mechanism has been proposed as shown in Scheme 1. Pre-catalyst [RhCp^*Cl₂]₂ is initially converted into an active cationic Rhodium species A by the action of AgSbF₆. A is directed to activate the ortho C-H bond in urea 1 to finish aryl Cp^*Rh (Ⅲ) species B which coordinates with alkyne 2 followed by migratory insertion giving alkenyl Cp^*Rh (Ⅲ) intermediate C. A second C-H bond activation event then took place intramolecularly leading to Rhodacycle D. A second insertion of alkyne molecule provide two possible Rhodacycles E or/and F and consequent reductive elimination delivers the homologated arene 3 and the reduced Cp^*Rh (Ⅰ) species is oxidized by Cu (Ⅱ) to regenerate Cp^*Rh (Ⅲ) complex A ready for a second catalytic circle.

  According to this mechanism, it can be deduced from the product structure of 3ab-3eb that D is formed favorably over D' from B and this is also in line with Fagnou's observations [11], where electronic effect was raised to explain this intrinsic regioselectivity. For the same reason, the second alkyne insertion will take place at one of the two C-Rh bonds of D to give preferentially E over E' and F over F', respectively. After reductive elimination, rhodacycle E will give the observed naphthalene 3aa, whereas F will give its regioisomer 3'aa which is not detected, disproving the intermediacy of rhodacycle F (Scheme 2). These analyses support a pathway B-C-D-E as the operating pathway shown in Scheme 1.

  Scheme 1

  

  图 Scheme 1  Proposed mechanism for the arene homologation (R_S stands for small group, R_L stands for large group).

  Scheme 1.  Proposed mechanism for the arene homologation (R_S stands for small group, R_L stands for large group).

  下载: 全尺寸图片 幻灯片

  Scheme 2

  

  图 Scheme 2  Discrimination of two possible pathways.

  Scheme 2.  Discrimination of two possible pathways.

  下载: 全尺寸图片 幻灯片

  The low yield associated with ortho-and para-substituted phenyl ureas when diphenyl acetylene 2a was used as condensation partner may derive from the serious steric repulsions in the intermediates along the pathway, such as indicated in G and H (Fig. 1). Those steric interactions can be relieved when diphenyl acetylene 2a was replaced by methyphenyl acetylene 2b to afford increased yield.

  图 1

  

  图 1  The steric repulsions in intermediates G and H leading to low yields.

  Figure 1.  The steric repulsions in intermediates G and H leading to low yields.

  下载: 全尺寸图片 幻灯片

  4.   Conclusion

  In summary, we have established a facile method for arene homologation of aryl urea with internal alkyne. This rhodium catalyzed transformation features a double C-H activation process and two successive completely regioselctive migratory insertions of unsymmetrical alkynes into Rhodium-carbon bonds enable this method particularly useful for poly-substituted polyarenes. Furthermore, a mechanism proposal has been discussed.

  Acknowledgments

  We are grateful for the National Natural Science Foundation of China (No. 21272077), the Natural Science Foundation of Jiangsu Province (No. BK20131143), Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) for financial support.

  Appendix A. Supplementary data

  Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.cclet.2016.05.011.

• 1. [1]

     J.Q. Yu, Z.J. Shi, C-H Activation, Top. Curr. Chem., 292, Springer GmbH, 2010.

  2. [2]

     Baudoin O.. Transition metal-catalyzed arylation of unactivated C (sp3)-H bonds[J]. Chem. Soc. Rev., 2011, 40:  4902-4911. doi: 10.1039/c1cs15058h

  3. [3]

     McMurray L., O'Hara F., Gaunt M.J.. Recent developments in natural product synthesis using metal-catalysed C-H bond functionalisation[J]. Chem. Soc. Rev., 2011, 40:  1885-1898. doi: 10.1039/c1cs15013h

  4. [4]

     Yan G., Wu X., Yang M.. Transition-metal-catalyzed additions of C-H bonds to C-X (X=N, O) multiple bonds via C-H bond activation[J]. Org. Biomol. Chem., 2013, 11:  5558-5578. doi: 10.1039/c3ob40652k

  5. [5]

     Cuesta L., Urriolabeitia E.P.. Coordination-directed metallation strategy for C-H functionalization[J]. RSC Catal. Ser., 2013, 11:  262-309.

  6. [6]

     Lyons T.W., Sanford M.S.. Palladium-catalyzed ligand-directed C H functionalization reactions[J]. Chem. Rev., 2010, 110:  1147-1169. doi: 10.1021/cr900184e

  7. [7]

     Guimond N., Fagnou K.. Isoquinoline synthesis via rhodium-catalyzed oxidative cross-coupling/cyclization of aryl aldimines and alkynes[J]. J. Am. Chem. Soc., 2009, 131:  12050-12051. doi: 10.1021/ja904380q

  8. [8]

     Guimond N., Gorelsky S.I., Fagnou K.. Rhodium (Ⅲ)-catalyzed heterocycle synthesis using an internal oxidant:improved reactivity and mechanistic studies[J]. J. Am. Chem. Soc., 2011, 133:  6449-6457. doi: 10.1021/ja201143v

  9. [9]

     Guimond N., Gouliaras C., Fagnou K.. Rhodium (Ⅲ)-catalyzed isoquinolone synthesis:the N O bond as a handle for C N bond formation and catalyst turnover[J]. J. Am. Chem. Soc., 2010, 132:  6908-6909. doi: 10.1021/ja102571b

  10. [10]

      Rousseaux S., Gorelsky S.I., Chung B.K.W., Fagnou K.. Investigationofthemechanism of C (sp³) H bond cleavage in Pd (0)-catalyzed intramolecular alkane arylation adjacent to amides and sulfonamides[J]. J. Am. Chem. Soc., 2010, 132:  10692-10705. doi: 10.1021/ja103081n

  11. [11]

      Stuart D.R., Alsabeh P., Kuhn M., Fagnou K.. Rhodium (Ⅲ)-catalyzed arene and alkene C H bond functionalization leading to indoles and pyrroles[J]. J. Am. Chem. Soc., 2010, 132:  18326-18339. doi: 10.1021/ja1082624

  12. [12]

      Stuart D.R., Bertrand M., Laperle -, Burgess K.M.N., Fagnou K.. Indole synthesis via rhodium catalyzed oxidative coupling of acetanilides and internal alkynes[J]. J. Am. Chem. Soc., 2008, 130:  16474-16475. doi: 10.1021/ja806955s

  13. [13]

      Liégault B., Fagnou K.. Palladium-catalyzed intramolecular coupling of arenes and unactivated alkanes in air[J]. Organometallics, 2008, 27:  4841-4843. doi: 10.1021/om800780f

  14. [14]

      Zhao D., Shi Z., Glorius F.. Indole synthesis by rhodium (Ⅲ)-catalyzed hydrazinedirected C-H activation:redox-neutral and traceless by N-N bond cleavage[J]. Angew. Chem. Int. Ed., 2013, 52:  12426-12429. doi: 10.1002/anie.201306098

  15. [15]

      Shi Z., Koester D.C., Boultadakis M., Arapinis -, Glorius F.. Rh (Ⅲ)-Catalyzed synthesis of multisubstituted isoquinoline and pyridine N-oxides from oximes and diazo compounds[J]. J. Am. Chem. Soc., 2013, 135:  12204-12207. doi: 10.1021/ja406338r

  16. [16]

      Al Mamari H.H., Diers E., Ackermann L.. Triazole-assisted ruthenium-catalyzed C[n.63743] H arylation of aromatic amides[J]. Chem. Eur. J., 2014, 20:  9739-9743. doi: 10.1002/chem.201403019

  17. [17]

      Li J., John M., Ackermann L.. Amidines for versatile ruthenium (Ⅱ)-catalyzed oxidative C-H activations with internal alkynes and acrylates[J]. Chem. Eur. J., 2014, 20:  5403-5408. doi: 10.1002/chem.v20.18

  18. [18]

      Ackermann L., Diers E., Manvar A.. Ruthenium-catalyzed C-H bond arylations of arenes bearing removable directing groups via six-membered ruthenacycles[J]. Org. Lett., 2012, 14:  1154-1157. doi: 10.1021/ol3000876

  19. [19]

      Liu W., Ackermann L.. Ortho-and para-selective ruthenium-catalyzed C (sp2)-H oxygenations of phenol derivatives[J]. Org. Lett., 2013, 15:  3484-3486. doi: 10.1021/ol401535k

  20. [20]

      Ma W., Graczyk K., Ackermann L.. Ruthenium-catalyzed alkyne annulations with substituted 1H-pyrazoles by C-H/N-H bond functionalizations[J]. Org. Lett., 2012, 14:  6318-6321. doi: 10.1021/ol303083n

  21. [21]

      Schinkel M., Wang L., Bielefeld K., Ackermann L.. Ruthenium (Ⅱ)-catalyzed C (sp3)-H α-alkylation of pyrrolidines[J]. Org. Lett., 2014, 16:  1876-1879. doi: 10.1021/ol500300w

  22. [22]

      Ciana C.L., Phipps R.J., Brandt J.R., Meyer F.M., Gaunt M.J.. A highly para-selective copper (Ⅱ)-catalyzed direct arylation of aniline and phenol derivatives[J]. Angew. Chem. Int. Ed., 2011, 5050:  458-462.

  23. [23]

      Haffemayer B., Gulias M., Gaunt M.J.. Amine directed Pd (ii)-catalyzed C-H bond functionalization under ambient conditions[J]. Chem. Sci., 2011, 2:  312-315. doi: 10.1039/C0SC00367K

  24. [24]

      Neufeldt S.R., Sanford M.S.. Asymmetric chiral ligand-directed alkene dioxygenation[J]. Org. Lett., 2012, 15:  46-49.

  25. [25]

      Yang G., Lindovska P., Zhu D.. Pd (Ⅱ)-catalyzed meta-C-H Olefination, arylation, and acetoxylation of indolines using a U-shaped template[J]. J. Am. Chem. Soc., 2014, 136:  10807-10813. doi: 10.1021/ja505737x

  26. [26]

      Shang M., Wang H.L., Sun S.Z., Dai H.X., Yu J.Q.. Cu (Ⅱ)-mediated ortho C-H alkynylation of (hetero) arenes with terminal alkynes[J]. J. Am. Chem. Soc., 2014, 136:  11590-11593. doi: 10.1021/ja507704b

  27. [27]

      Tang R.Y., Li G., Yu J.Q.. Conformation-induced remote meta-C-H activation of amines[J]. Nature, 2014, 507:  215-220. doi: 10.1038/nature12963

  28. [28]

      ChanKelvin S.L., Wasa M., Chu L.. Ligand-enabled cross-coupling of C (sp3)-H bonds with arylboron reagents via Pd (Ⅱ)/Pd (0) catalysis[J]. Nat. Chem., 2014, 6:  146-150. doi: 10.1038/nchem.1836

  29. [29]

      Zhang G., Yang L., Wang Y., Xie Y., Huang H.. An Efficient Rh/O₂ catalytic system for oxidative C-H activation/annulation:evidence for Rh (I) to Rh (Ⅲ) oxidation by molecular oxygen[J]. J. Am. Chem. Soc., 2013, 135:  8850-8853. doi: 10.1021/ja404414q

  30. [30]

      Wang C., Huang Y.. Traceless directing strategy:efficient synthesis of N-alkyl indoles via redox-neutral C-H activation[J]. Org. Lett., 2013, 15:  5294-5297. doi: 10.1021/ol402523x

  31. [31]

      Chan W.W., Lo S.F., Zhou Z., Yu W.Y.. Rh-catalyzed intermolecular carbenoid functionalization of aromatic C-H bonds by a-diazomalonates[J]. J. Am. Chem. Soc., 2012, 134:  13565-13568. doi: 10.1021/ja305771y

  32. [32]

      Liu B., Song C., Sun C., Zhou S., Zhu J.. Rhodium (Ⅲ)-catalyzed indole synthesis using N-N bond as an internal oxidant[J]. J. Am. Chem. Soc., 2013, 135:  16625-16631. doi: 10.1021/ja408541c

  33. [33]

      Huang X.C., Yang X.H., Song R.J., Li J.H.. Rhodium-catalyzed synthesis of isoquinolines and indenes from benzylidenehydrazones and internal alkynes[J]. J. Org. Chem., 2014, 79:  1025-1031. doi: 10.1021/jo402497v

  34. [34]

      Wang N.J., Mei S.T., Shuai L., Yuan Y., Wei Y.. Aerobic oxidative C-H olefination of cyclic N-sulfonyl ketimines catalyzed by a rhodium catalyst[J]. Org. Lett., 2014, 16:  3040-3043. doi: 10.1021/ol501152a

  35. [35]

      Sun H., Wang C., Yang Y.F.. Synthesis of indolo[2, 1-a]isoquinolines via a triazene-directed C-H annulation cascade[J]. J. Org. Chem., 2014, 79:  11863-11872. doi: 10.1021/jo500807d

  36. [36]

      Han W., Zhang G., Li G., Huang H.. Rh-catalyzed sequential oxidative C-H and N-N bond activation:conversion of azines into isoquinolines with air at room temperature[J]. Org. Lett., 2014, 16:  3532-3535. doi: 10.1021/ol501483k

  37. [37]

      Chuang S.C., Gandeepan P., Cheng C.H.. Synthesis of isoquinolines via Rh (Ⅲ)-catalyzed C-H activation using hydrazone as a New oxidizing directing group[J]. Org. Lett., 2013, 15:  5750-5753. doi: 10.1021/ol402796m

  38. [38]

      Li G., Ding Z., Xu B.. Rhodium-catalyzed oxidative annulation of sulfonylhydrazones with alkenes[J]. Org. Lett., 2012, 14:  5338-5341. doi: 10.1021/ol302522n

  39. [39]

      Song Z., Samanta R., Antonchick A.P.. Rhodium (Ⅲ)-catalyzed direct regioselective synthesis of 7-substituted indoles[J]. Org. Lett., 2013, 15:  5662-5665. doi: 10.1021/ol402626t

  40. [40]

      Houlden C.E., Bailey C.D., Ford J.G.. Distinct reactivity of Pd (OTs)2:the intermolecular Pd (Ⅱ)-catalyzed 1, 2-carboamination of dienes[J]. J. Am. Chem. Soc., 2008, 130:  10066-10067. doi: 10.1021/ja803397y

  41. [41]

      Anthony J.E.. Functionalized acenes and heteroacenes for organic electronics[J]. Chem. Rev., 2006, 106:  5028-5048. doi: 10.1021/cr050966z

  42. [42]

      Bendikov M., Wudl F., Perepichka D.F.. Tetrathiafulvalenes, oligoacenenes, and their buckminsterfullerene derivatives:the brick and mortar of organic electronics[J]. Chem. Rev., 2004, 104:  4891-4945. doi: 10.1021/cr030666m

  43. [43]

      Cicoira F., Santato C.. Organic light emitting field effect transistors:advances and perspectives[J]. Adv. Funct. Mater., 2007, 17:  3421-3434. doi: 10.1002/(ISSN)1616-3028

  44. [44]

      Sundar V.C., Zaumseil J., Podzorov V.. Elastomeric transistor stamps:reversible probing of charge transport in organic crystals[J]. Science, 2004, 303:  1644-1647. doi: 10.1126/science.1094196

  45. [45]

      Watanabe M., Chen K.Y., Chang Y.J., Chow T.J.. Acenes generated from precursors and their semiconducting properties[J]. Acc. Chem. Res., 2013, 46:  1606-1615. doi: 10.1021/ar400002y

  46. [46]

      Kitamura C., Ohara T., Yoneda A.. Synthesis and solid-state optical properties of 2, 3-dialkyl-and 2, 3, 8, 9-tetraalkyltetracenes[J]. Chem. Lett., 2011, 40:  58-59. doi: 10.1246/cl.2011.58

  47. [47]

      Paraskar A.S., Reddy A.R., Patra A.. Rubrenes:planar and twisted[J]. Chem. Eur. J., 2008, 14:  10639-10647. doi: 10.1002/chem.200800802

  48. [48]

      Qiao X., Padula M.A., Ho D.M.. Octaphenylnaphthalene and decaphenylanthracene[J]. J. Am. Chem. Soc., 1996, 118:  741-745. doi: 10.1021/ja953669s

  49. [49]

      Takahashi T., Li S., Huang W.. Homologation method for preparation of substituted pentacenes and naphthacenes[J]. J. Org. Chem., 2006, 71:  7967-7977. doi: 10.1021/jo060923y

  50. [50]

      Huang W., Zhou X., Kanno K.I., Takahashi T.. Pd-Catalyzed reactions of o-diiodoarenes with alkynes for aromatic ring extension[J]. Org. Lett., 2004, 6:  2429-2431. doi: 10.1021/ol049176m

  51. [51]

      Pellissier H., Santelli M.. The use of arynes in organic synthesis[J]. Tetrahedron, 2003, 59:  701-730. doi: 10.1016/S0040-4020(02)01563-6

  52. [52]

      Pena D., Perez D., Guitian E., Castedo L.. Palladium-catalyzed cocyclization of arynes with alkynes:selective synthesis of phenanthrenes and naphthalenes[J]. J. Am. Chem. Soc., 1999, 121:  5827-5828. doi: 10.1021/ja9907111

  53. [53]

      Seri T., Qu H., Zhou L., Kanno K.i., Takahashi T.. Substituent effects in the preparation of naphthacenes by the coupling reaction of diyne-derived zirconacyclopentadienes with tetraiodobenzene[J]. Chem. Asian J., 2008, 3:  388-392. doi: 10.1002/asia.v3:2

  54. [54]

      Takahashi T., Li Y., Stepnicka P.. Coupling reaction of zirconacyclopentadienes with dihalonaphthalenes and dihalopyridines:a new procedure for the preparation of substituted anthracenes, quinolines, and isoquinolines[J]. J. Am. Chem. Soc., 2002, 124:  576-582. doi: 10.1021/ja016848k

  55. [55]

      Yoshikawa E., Radhakrishnan K.V., Yamamoto Y.. Palladium-catalyzed controlled carbopalladation of benzyne[J]. J. Am. Chem. Soc., 2000, 122:  7280-7286. doi: 10.1021/ja001205a

  56. [56]

      Adak L., Yoshikai N.. Iron-catalyzed annulation reaction of arylindium reagents and alkynes to produce substituted naphthalenes[J]. Tetrahedron, 2012, 68:  5167-5171. doi: 10.1016/j.tet.2012.04.004

  57. [57]

      Bej A., Chakraborty A., Sarkar A.. Solvent free, phosphine free Pd-catalyzed annulations of aryl bromides with diarylacetylenes[J]. RSC Adv., 2013, 3:  15812-15819. doi: 10.1039/c3ra41924j

  58. [58]

      Fukutani T., Hirano K., Satoh T., Miura M.. Synthesis of highly substituted acenes through rhodium-catalyzed oxidative coupling of arylboron reagents with alkynes[J]. J. Org. Chem., 2011, 76:  2867-2874. doi: 10.1021/jo200339w

  59. [59]

      Kawasaki S., Satoh T., Miura M., Nomura M.. Synthesis of tetrasubstituted naphthalenes by palladium-catalyzed reaction of aryl iodides with internal alkynes[J]. J. Org. Chem., 2003, 68:  6836-6838. doi: 10.1021/jo0346656

  60. [60]

      Komeyama K., Kashihara T., Takaki K.. Cobalt-catalyzed annulation of aryl iodides with alkynes[J]. Tetrahedron Lett., 2013, 54:  5659-5662. doi: 10.1016/j.tetlet.2013.07.133

  61. [61]

      Pham M.V., Cramer N.. Aromatic homologation by non-chelate-assisted Rh (Ⅲ)-catalyzed C-H functionalization of arenes with alkynes[J]. Angew. Chem. Int. Ed., 2014, 53:  3484-3487. doi: 10.1002/anie.201310723

  62. [62]

      Misal Castro L.C., Obata A., Aihara Y., Chatani N.. Chelation-assisted nickelcatalyzed oxidative annulation via double C H activation/alkyne insertion reaction[J]. Chem. Eur. J., 2016, 22:  1362-1367. doi: 10.1002/chem.v22.4

  63. [63]

      Shi Z., Tang C., Jiao N.. Chemoselective synthesis of naphthylamides and isoquinolinones via rhodium-catalyzed oxidative dehydrogenative annulation of benzamides with alkynes[J]. Adv. Synth. Catal., 2012, 354:  2695-2700. doi: 10.1002/adsc.v354.14/15

  64. [64]

      Wu J., Cui X., Mi X., Li Y., Wu Y.. Palladium catalyzed synthesis of highly substituted naphthalenes via direct ring construction from amides with alkynes[J]. Chem. Commun., 2010, 46:  6771-6773. doi: 10.1039/c0cc01448f

  65. [65]

      Yamashita M., Horiguchi H., Hirano K., Satoh T., Miura M.. Fused ring construction around pyrrole, indole, and related compounds via palladium-catalyzed oxidative coupling with alkynes[J]. J. Org. Chem., 2009, 74:  7481-7488. doi: 10.1021/jo9016698

  66. [66]

      Stuart D.R., Bertrand-Laperle M., Burgess K.M.N., Fagnou K.. Indole synthesis via rhodium catalyzed oxidative coupling of acetanilides and internal alkynes[J]. J. Am. Chem. Soc., 2008, 130:  16474-16475. doi: 10.1021/ja806955s

  67. [67]

      Larock R.C., Yum E.K., Refvik M.D.. Synthesis of 2, 3-disubstituted indoles via palladium-catalyzed annulation of internal alkynes[J]. J. Org. Chem., 1998, 63:  7652-7662. doi: 10.1021/jo9803277

  68. [68]

      Li L., Brennessel W.W., Jones W.D.. C-H activation of phenyl imines and 2-phenylpyridines with[Cp^*MCl₂]₂(M=Ir, Rh):regioselectivity, kinetics, and mechanism[J]. Organometallics, 2009, 28:  3492-3500. doi: 10.1021/om9000742

  69. [69]

      Ueura K., Satoh T., Miura M.. Rhodium-and iridium-catalyzed oxidative coupling of benzoic acids with alkynes via regioselective C-H bond cleavage[J]. J. Org. Chem., 2007, 72:  5362-5367. doi: 10.1021/jo070735n

  70. [70]

      Ueura K., Satoh T., Miura M.. An efficient waste-free oxidative coupling via regioselective C-H Bond Cleavage:Rh/Cu-catalyzed reaction of benzoic acids with alkynes and acrylates under air[J]. Org. Lett., 2007, 9:  1407-1409. doi: 10.1021/ol070406h

• 

  Scheme 1  Proposed mechanism for the arene homologation (R_S stands for small group, R_L stands for large group).

  下载: 全尺寸图片 幻灯片
  

  Scheme 2  Discrimination of two possible pathways.

  下载: 全尺寸图片 幻灯片
  

  Figure 1  The steric repulsions in intermediates G and H leading to low yields.

  下载: 全尺寸图片 幻灯片

  Table 1.  Condition optimization for oxidative condensation of phenyl urea with alkyne.^a

  下载: 导出CSV

  Table 2.  Arene homologation of aryl ureas with dipenyl acetylene.^a

  下载: 导出CSV

  Table 3.  Arene homologation of aryl ureas with unsymmetrical acetylenes.^a

  下载: 导出CSV
•