The work described falls into two parts, the synthesis of chiral cyclobutenes and of
cyclopropanes obtained from terpenes. The first part of the work sought to develop a simple
route for the synthesis of new cyclobutene containing building blocks as single enantiomers
by a ring expansion of a cyclopropylchlorocarbenes and an examination of how to control
these processes to give only, or largely, one product.
Most attention was given to understanding the effect of a substituent (R) on the migration
selectivity of the carbene, two geometries of carbene and two migrations routes being
possible. A number of chlorocyclobutenes (B) and (C) containing chiral building blocks
were prepared from dichloromethylcyclopropanes using potassium tert-butoxide to give the
carbene (A).
It was found that the carbene rearranged with different substitutents (R) all gave two
isomers of cyclobutene though in different ratios.
The second part of the work led to the preparation of an enantiomerically pure cyclopropene
(G) starting from dihalocarbene adducts of linalyl acetate (D) or linalool (E), which after hydrodehalogenation to mixtures of four isomers (F) then underwent dehydrohalogenation
of (F) to give the single cyclopropene (G). The cyclopropene (G) rearranged to vinylketone (I) under mild conditions. Some reactions of (I) were examined.