Highly stereoselective reaction ofα-methylthio aldehydes with allyltriphenylstannane: Synthesis of anti-β-methylthio alcohols

✍ Scribed by Masayuki Shimagaki; Hideki Takubo; Takeshi Oishi

• Publisher: Elsevier Science
• Year: 1985
• Tongue: French
• Weight: 217 KB
• Volume: 26
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)95061-5

✦ Synopsis

The reaction of a-methylthio aldehydes 4(R=1°, 2') with allyltriphenylstannane 5 in the presence of SnC14 gave anti-8-methylthio alcohols 6 in excellent selectivity.

In connection with the recent findings that conversion of B-alkylthio alcohols 2 and 3 into olefins' or epoxides 2 proceeds with complete stereospecificity, we examined the synthesis of the stereochemically pure 2 and 3 by reduction of the corresponding a-methylthio or a-phenylthio ketones 1 and found that Z'n(BH4)2 reduction gave the expected anti-3(chelation-controlled products) only in limited cases, while L-Selectride reduction afforded syn-2 (non-chelation-controlled Felkin-Anh products) with remarkably high stereoselectivity in every case, except when R1 was secondary.3 These results are in sharp contrast with those obtained in the reduction of a-alkoxy ketones.4 The poor anti-selectivity observed in Zn(BH4)2 reaction could be ascribed to weaker affinity of sulfur than oxygen to Zn2+ and excellent synselectivity observed in L-Selectride reduction to a large contribution of a methylthio group in stabilizing a Felkin-Anh model.5