Claisen Rearrangements of Allylic and Propargylic Alcohols Prepared by an N-Boc-2-acyloxazolidine Methodology − Application to the Synthesis of Original Chiral Building Blocks
protecting group occurs stereoselectively. The resulting α,β-epoxyoxazolidines are then transformed into trisubstituted stereodefined cyclopropanes. Claisenrearrangements of propargylic alcohols, on the other hand, stereoselectively give α-allenyloxazolidines. These compounds follow a different pathway to α-alkenyloxazolidines as regards bromocarbamation. An original route to enantiopure 3-hydrox
stereodefined propargylic or allylic alcohol side chain were transformed into the corresponding mesylates. Alkylation of these allylic mesylates by means of organocuprate reagents effected a regio and stereoselective 1,3-transfer of chirality. Similarly, alkylation of the propargylic mesylate gave a chiral allenyl oxazolidine. The N-Boc-2-alkenyl oxazolidines resulting from an anti SN2′ addition underwent an