Enantioselective Addition of Aromatic Thiols to a Ketene

✍ Scribed by Dr. Charles Fehr; Dr. Isabelle Stempf; José Galindo

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 394 KB
• Volume: 32
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.199310441

✦ Synopsis

A solution of(R.S)-4 (40.0 g, 153.8 mmol) in THF(450 mL) wascooled at -100 to -110 C (Et,O, liquid N,) and treated with 1.92 M nBuLi in hexane (120.2 mL, 230.8 mmol) (40 min. T 5 -100 C). The solution was stirred hetween -105 and -100 C for 2 h. A solution of (-)-7 (63.7 g, 307.7 mmol) in T H F (100 mL) was then added over 50 min at -100 ,C. The reaction mixture was cooled to between -102 and -100 C for 1 h and than allowed to warm up to -10 Cover 25 min. The mixture was poured into vigorously stirred 5% aq NaOH and extracted with Et,O. The organic phase was washed successively with H,O, 5% aq HCI. H,O. Saturated NaHCO,, and saturated NaCl solution, dried over Na,SO,, and concentrated. Distillation (1 lO-C!0.02 Torr) afforded c = 0.04). The combined acidic aqueous phases were hasified (10% KOH). extracted (Et20). and distilled 90'Ci2 Torr) to afford recovered (-)-7 (62.4 g. 98%). -(S)-4: 'H NMR (360 MHz. CDCI,, 25.C): 6 = 0.96(s. 3 H): 1.05 (s, 3 H ) ; l Zl(m.1 H),1.79(hr.s.3H),I.91(m.l H).1.98-2.lX(m.2H),2.X6(br. s. 1 H), 5.64 (hr. s, 1 H). 7.38 (s. 5 H). IR (neat): F = 2970. 1705. 14x0. 1440, 980cm-'. MS (70eV): nz/z(%): 151 (13). 123 (100). 109(12), 107(10). 91 (9). 81 (33). ( R ) -4 ( ~9 7 % p u r e h y G C ; Y 9 % ~~. e [ 1 2 ] , [ 1 ] ~0 = + 427(CHCI,.c =0.06))was obtained accordingly when (+)-7 was used.

(S)-4 (34.92 g, 87%. 2 9 7 % hy GC. 99% ce [12]. [XI;"=- 421 (CHCI,,