Alternatively the same objective can be accomplished using Petasis reagent. It is synthesized by treating titanocene chloride with methyl lithium (Scheme 17). It shows reactivity similar to Tebbe's reagent. Petasis reagents can methyleneate ketones, aldehydes and esters on thermolysis at 60°C.

Scheme 17

McMurry reaction is used to synthesize alkenes from dicarbonyl compounds (Scheme 18). This reaction first generates an intermediate 1,2-diol which is then dehydrated on the surface of titanium to form alkene. However, the reaction is not stereospecific since the two the carbon-oxygen bonds do not break simultaneously. In case of cyclic 1,2-diols, a titanocycle has to be formed for this reaction to occur. Thus, trans diols are inert under these conditions.

Scheme 18

This methodology may be extended to ketoesters, where cyclic enol ether is formed which on hydrolysis forms the corresponding cycloalkanone (Scheme 19).

Scheme 19

Text Book

M. B. Smith, Organic Synthesis , McGraw Hill, Singapore, 2004.