Cycloaddition and Electrocyclic Reactions of Vinylketenes, Allenylketenes, and Alkynylketenes

Vinylketenes may be prepared by the typical procedures used for other ketenes, and are usually highly reactive, except when bulky groups and silyl substituents are present. They are extensively utilized in cycloaddition reactions and electrocyclizations, including dimerizations, inter- and intramolecular reactions with alkenes, alkynes, imines, and carbonyl groups, and intramolecular reactions with aryl and heteroaryl groups. These pericyclic reactions are widely used in syntheses of carbocyclic and heterocyclic products, and are particularly useful for the preparation of β-lactams and β-lactones. Allenylketenes and alkynylketenes also undergo cycloaddition and electrocyclic reactions. Keywords: Vinylketenes; allenylketenes; alkynylketenes; cycloaddition; electrocyclization; diazo ketones; cyclobutenones; cyclohexadienones; acyl chlorides; β-lactams; β-lactones