Synthesis of Ketones

Many of the carbonylative routes to ketones are closely related to those described in the previous chapter for the synthesis of aldehydes, with the obvious difference that a carbanion or carbonium ion source is now required in place of a hydride or proton donor. Favored starting materials are again halocarbons, alkenes, or alkynes, which are readily carbonylated to a range of symmetrical, unsymmetrical, or cyclic ketones. For example, one of the most intensively studied reactions of this type has been the catalytic coupling of an alkene with carbon monoxide and an alkyne. This leads to compounds containing the α,β-unsaturated cyclopentenone skeleton, and the reaction has been exploited in the synthesis of a series of natural products. In view of the importance of cyclocarbonylation, a separate section of this chapter is devoted to the synthesis of cyclic ketones.