Ketone Methylenation Using the Tebbe and Wittig Reagents - A Comparison

Ketone methylenation has been accomplished using the Tebbe and the Wittig reagents. Comparison of the two reagents for a variety of ketones shows that the Tebbe reagent gives better product yields than the Wittig reagent. This is particularly important when the ketone substrate is hindered. It is also noted that the Tebbe reaction accomplishes methylenation in a non-basic medium, thus racemization does not take place on substrates with enolizable chiral centers.