A method for the [2 + 2] cycloaddition of aryl ketenes and alkenes is presented. The process involves the in situ generation of a ketene in the presence of a Lewis acid. The utility of products is demonstrated towards the synthesis of a common scaffold found in several natural product families.

Ab inido molecular orbital ealenlations with large, polarizetion basis sets and incorporating valence electron correlation have been employed to examine the [GHzO]+' potential energy snrface. Four [WzO1+' isomers have been identified as potentially stable, observable ions. T h e are the experimentdly well-known ketene radical cation, [CH4=0 ]+ ' (a), and tbe presently unlmown ethynol radical ca...

(Z)-Selective olefination of several lactones with ketene silyl acetals was achieved by the catalysis of carbon acids (C-H acids) having a bis(triflyl)methyl group as an acidic functionality; in particular, the triple carbon acid having three bis(triflyl)methyl groups in phloroglucinol shows an excellent catalytic performance.

The conversion of a substituted dioxinone to a pyrone was used in an improved synthesis of the AB spiroketal subunit of the spongistatins. This transformation occurred via a hetero-Diels-Alder reaction of an acyl ketene with butyl vinyl ether. A double diastereoselective Mukaiyama aldol reaction is used to provide the hetero-Diels-Alder precursor.