Silyl Cyanopalladate-Catalyzed Friedel–Crafts-Type Cyclization Affording 3-Aryloxindole Derivatives

Abstract

3-Aryloxindole derivatives were synthesized through a Friedel–Crafts-type cyclization. The reaction was catalyzed by a trimethylsilyl tricyanopalladate complex generated in situ from trimethylsilyl cyanide and Pd(OAc)₂. Wide varieties of diethyl phosphates derived from N-arylmandelamides were converted almost quantitatively into oxindoles. When N,N-dibenzylamide was used instead of an anilide substrate, a benzo-fused δ-lactam was obtained. An oxindole product was subjected to substitution reactions to afford 3,3-diaryloxindoles with two different aryl groups.

Key words

Lewis acid catalysis - Friedel–Crafts reaction - cyclization - oxindoles - S_N1 reaction

• References and Notes

• 1 Uddin MK, Reignier SG, Coulter T, Montalbetti C, Grånäs C, Butcher S, Krong-Jensen C, Felding J. Bioorg. Med. Chem. Lett. 2007; 17: 2854
• 2a Hewawasam P, Gribkoff VK, Pendri Y, Dworetzky SI, Meanwell NA, Martinez E, Boissard CG, Post-Munson DJ, Trojnacki KT, Yeleswaram K, Pajor LM, Knipe J, Gao Q, Perrone R, Starrett JE. Jr. Bioorg. Med. Chem. Lett. 2002; 12: 1023
• 2b Shibata N, Ishimaru T, Suzuki E, Kirk KL. J. Org. Chem. 2003; 68: 2494
• 3a Nagamine J, Nagata R, Seki H, Nomura-Akimaru N, Ueki Y, Kumagai K, Taiji M, Noguchi H. J. Endocrinol. 2001; 171: 481
• 3b Tomita D, Yamatsugu K, Kanai M, Shibasaki M. J. Am. Chem. Soc. 2009; 131: 6946
• 4 Chowdhury S, Chafeev M, Liu S, Sun J, Raina V, Chui R, Young W, Kwan R, Fu J, Cadieux JA. Bioorg. Med. Chem. Lett. 2011; 21: 3676
• 5a Trost BM, Brennan MK. Synthesis 2009; 3003
• 5b Kaur M, Singh M, Chadha N, Silakari O. Eur. J. Med. Chem. 2016; 123: 858
• 6a Shaughnessy KH, Hamann BC, Hartwig JF. J. Org. Chem. 1998; 63: 6546
• 6b Lee S, Hartwig JF. J. Org. Chem. 2001; 66: 3402
• 6c Ackermann L, Vicente R, Hofmann N. Org. Lett. 2009; 11: 4274
• 7a Rey V, Pierini AB, Peñéñory AB. J. Org. Chem. 2009; 74: 1223
• 7b Soria-Castro SM, Caminos DA, Peñéñory AB. RSC Adv. 2014; 4: 17490

Under the photoirradiation conditions, the S_RN1-reaction of o-chloroanilides affords the 3-aryloxindole derivatives, see:
• 8a Wolfe J, Sleevi MC, Goehring RR. J. Am. Chem. Soc. 1980; 102: 3646
• 8b Goehring RR, Sachdeva YP, Pisipati JS, Sleevi MC, Wolfe JF. J. Am. Chem. Soc. 1985; 107: 435
• 9 Beyer A, Buendia J, Bolm C. Org. Lett. 2012; 14: 3948
• 10 Lai P.-S, Dubland JA, Sarwar MG, Chudzinski MG, Taylor MS. Tetrahedron 2011; 67: 7586
• 11 Yurino T, Tani R, Ohkuma T. ACS Catal. 2019; 9: 4434
• 12 Yurino T, Tange Y, Tani R, Ohkuma T. Org. Chem. Front. 2020; 7: 1308
• 13 Yurino T, Ece H, Ohkuma T. Asian J. Org. Chem. 2020; 9: 557
• 14 1-Methyl-3-phenyl-1,3-dihydro-2H-indol-2-one (2a): Typical Procedure A 20 mL Schlenk flask was charged with diethyl 2-[methyl(phenyl)amino]-2-oxo-1-phenylethyl phosphate (1a: 130 mg, 0.35 mmol). Pd(OAc)₂ (1.6 mg, 7.0 μmol) was added, and the flask was subjected to three evacuation–argon replacement cycles. MeNO₂ (2.0 mL) was added, and the solution was stirred for 15 min at 60 °C. TMSCN (71 mg, 0.72 mmol) was then added, and the mixture was stirred at 60 °C for 10 h until the reaction was complete [TLC, hexane–EtOAc (4:1)]. The reaction was quenched with sat. aq NaHCO₃, and the aqueous layer was extracted with EtOAc (3 × 10 mL). The collected organic layers were washed with brine, dried (Na₂SO₄), filtered, and concentrated in vacuo. The yield of the product (>99%) was determined from the ¹H NMR spectrum of the crude product, with pyrazine as an internal standard. The product was isolated by preparative TLC (hexane–EtOAc, 4:1) as a white solid; yield: 76 mg (0.34 mmol, 98%); mp 126–132 °C. ¹H NMR (400 MHz, CDCl₃): δ = 7.36–7.28 (m, 4 H, Ar-H), 7.22–7.16 (m, 3 H, Ar-H), 7.07 (t, J = 7.6 Hz, 1 H, Ar-H), 6.91 (d, J = 7.6 Hz, 1 H, Ar-H), 4.62 (s, 1 H, CH), 3.26 (s, 3 H, NCH₃). ¹³C NMR (100 MHz, CDCl₃): δ = 176.0, 144.4, 136.6, 128.83, 128.79, 128.4 (two overlapping peaks), 127.5, 125.0, 122.7, 108.1, 52.0, 26.4.
• 15 Mai C.-K, Sammons MF, Sammakia T. Org. Lett. 2010; 12: 2306