Printed in Great Britain. (0 1996 IUPAC Organotitanium compounds in organic synthesis

Abstract: Mild thermolysis of diakyltitanocenes can generate a reactive titanocene alkylidene species which in situ convert a variety of carbonyl compounds to the corresponding olefm. They also react with nitriles and alkynes and can serve as initiators of ring-opening metathesis polymerization. The olefination process mediated by these compounds is mild, experimentally convenient and works with many types of carbonyls, including: aldehydes, ketones, esters, lactones, silyl esters, anhydrides, carbonates, amides, lactams, hides, thioesters, selenoesters and acyl silanes. This olefination can be combined with subsequent transformations to produce carbocycles and heterocycles. Olefination of 1,3-dioxolan-4-ones followed by an aluminum-mediated rearangement gives temhydrofurans, while a similar sequence with 1,3-dioxan-4-0nes gives tetrahydropyrans in a highly stereocontrolled manner