Synthesis and Properties of Functionalized 2,4‐Ethano‐Bridged Bicyclobutanes

Starting from 1,2,4,5,6‐pentamethyl‐3‐methylenetricyclo[3.1.0.0 2.6 ]‐ hexane ( 3 ), a number of functionalized ethano‐bridged bicyclobutanes have been prepared. Ozonolysis of the carbon‐carbon double bond of compound 3 leads to the strained and sterically hindered ketone 4 which can be further transformed into tricyclic alcohols and azines. The formation of the rearranged lactone 19 in the oxidation of ketone 4 with O 3 or peracid is in agreement with a mechanism in which the 1,2‐alkyl shift from carbon to oxygen occurs by way of a β‐fission followed by a recombination step. Treatment of the dichlorocarbene adduct of alkene 3 with n‐BuLi afforded allene 7 , which on reaction with TCNE yielded a di‐ cis ‐fused cyclopropane.