Abstract
The facial diastereoselectivity in the photocycloaddition of the chiral N-acyl enamines 5, 6, and 7 to benzaldehyde has been studied. The anamide 5 derived from α-phenylethylamine (8) gave the corresponding oxetanes in good total yield (74%) but the diastereofacial selection was unsatisfactory (32% de). The N-vinyloxazolidinones 6 and 7 were prepared from the parent chiral 4-phenyl- (11) or 4-benzyloxazolidinone (15) by vinylation. Their photocycloadditons to benzaldehyde proceeded smoothly and yielded the corresponding oxetanes 12 and 16 (70-80%). A remarkable discrepancy in the course of the reaction was observed. Whereas oxetane formation from 6 proceeded with low diastereoselectivity (30% de) the Paterno-Buchi reaction of compound 7 gave predominantly one diastereoisomer 16a (62% de) the relative configuration of which was opposite to the major diastereomer 12a obtained from oxazolidinone 6.
Original language | English |
---|---|
Pages (from-to) | 4507-4520 |
Number of pages | 14 |
Journal | Tetrahedron |
Volume | 54 |
Issue number | 18 |
DOIs | |
State | Published - 30 Apr 1998 |
Externally published | Yes |