Remarkable increase in the diastereofacial selectivity of the addition of β-methyl α-(alkoxy)allylstannane to aldehydes: substituent effects on diastereofacial selectivity

✍ Scribed by Benjamin W Gung; Daniel T Smith; Mark A Wolf

• Publisher: Elsevier Science
• Year: 1991
• Tongue: French
• Weight: 260 KB
• Volume: 32
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)71205-6

✦ Synopsis

Several new chiral allylstannanes were prepared and reacted with aldehydes. Excellent diastereofacial selectivity was observed for the reactions of allylstannane 1 with aldehydes in the presence of BFs*EtzO. This is in contrast to the results from other allylstannanes which do not bear a emethyl group.

These observations were rationalized based on a combination of steric and electronic effects.

The reaction of crotylstannanes with aldehydes in the presence of BF3*Et20 affords stemochemically defined building blocks for natural product synthesis. 1 A sufficient number of applications have appeared to provide good documentation for predicting a high syn-selective addition in these reactions2. Recent studies by Marshall on a-(alkoxy)allylstannanes showed that asymmetric induction on achiral aldehydes can be realized by using enantiopum allylstannanes3. Unfortunately, although the simple diastereoselectivity (syn/anti) was high the diastereofacial selectivity was only modest. The factors that control the stereochemistry of the reactions between