STEREOSELECTIVE DIAZOALKANE CYCLOADDITIONS TO CHIRAL 5-ALKYLIDENE-1,3-DIOXAN-4-ONES AND 3-BENZYLIDENE-BETA-LACTONES

Stereoselective 1,3-dipolar cycloaddition of diazoalkanes to (E)-5-alk ylidene-1,3-dioxan-4-ones 1 and the (Z)-isomers (Z)-1 afforded spiropy razolines 3 and 10, respectively. The optically active 2-benzylidene-3 -methyl-beta-lactone (8) was synthesized from the corresponding 5-benz ylidene-1,3-dioxan-4-one 1f by hydrolysis and recyclization and added diazomethane with stereodifferentiation. Photochemical elimination of nitrogen from spiropyrazolines 3 gave enantiomerically pure spirocyclo propanes 12 that could be further transformed to cyclopropanecarboxyli c acids 13 and derivatives 14.