Regioselective Pinacol Rearrangement of Unsymmetrical Cyclobutane-1,2-diols

Abstract

Abstract Hydroxy-sulfone 34b, prepared as a mixture of trans and cis isomers by condensing the O-silyl derivative 18c of 2-hydroxy-2-methyl-cyclobutanone 18b — the Norrish II photocyclisation product of 2,3-pentanedione 21 — and methyl phenyl sulfone 33 was found to rearrange selectively either to the cyclopropanic β-ketosulfone 37 or the isomeric methyl ketone 38 by using, respectively, the tosyl fluoride/DBU and the DAST reagent. The potential of this methodology has been illustrated by a synthesis of phytal 1 from geranylacetone 46, and by the preparation from 3,4-hexanedione 51 and prenol 56 — via the cyclopropanic β-ketosulfone 54 (X-ray) — of an advanced fragment of the juvenile hormone molecule 59.