Carbonyl ylides directed syntheses

The formation of the naphthalene (73) from the bis-ylide (72) and diethyl ketomalonate involves an unusual olefin synthesis on the carbonyl of an ester group. The methylene-pyrans (75) were formed when the diethyl malonates (74) were refluxed with j3-keto-ylides in xylene or decalin. Possible intermediates are the ketens (76) and the allenes (77). Addition of ylide to the allenes gives the betaines (78) which form methylene-pyrans either directly or via acetylenes as shown. 

Maulide et al. developed a unified method for the direct transfer of ylides and the metal-free arylation of carbonyl compounds. This was applied in the synthesis of pyrrole 76 from 75 upon treatment with Martin s sulfurane in toluene at room temperature. The dearomatization of both indole and pyrrole could be effected with a variety of electron-donating or -withdrawing groups in good to excellent yields (13JA7312). 

Reactions.—The reaction of sulphonium ylides with carbonyl compounds to form oxirans is now a standard reaction. Among the more unusual examples reported are an intramolecular version directed towards the preparation of arene epoxide (12) (not isolable), the synthesis of the epoxide of 8-phenylthio-methylenecycloheptane, and the direct conversion of a diketone by dimethyl-sulphonium methylide into a doubly homologated hydroxymethyl aldehyde (13) by the rearrangement shown. ... 

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