Five-membered rings 2- acrylonitrile

Several moihanistic studies on the reactivity of sulphur-containing quinquevalent phosphorus acids have been recorded. The reactions investigated include addition to keten acetals, protodemetallation with tetraethylstannane, addition to methyl propiolate (for which there is c/j-addition in propanol but a lack of stereospecificity in aprotic media), and addition to acrylonitrile, with which five-membered-ring acids react faster than six-membered, which in turn react faster than acyclic acids. 

Similar 1,4-bis-silylation of a,p-unsaturated ketones with 32 is catalyzed by the isonitrile-palladium catalyst 34 to afford seven-membered ring silyl enol ether 69 in high yields (Eq. 35). Reactions of 32 with acrylic esters and acrylonitrile, however, give five-membered products 70 [20,30]. 

Two-carbon ring expansions of the five-, six,- and seven-membered rings of P-indanone, P-tetralone, and P-suberone can be achieved via a sensitized [2-1-2]-photoaddition of the trimethylsilyl enol ethers of the cyclic ketones with acrylonitrile or methyl acrylate followed by P-fragmentation of the alkoxyl radicals generated from the hypoiodites of the resulting cyclobutanols and mercury(ll) oxide-iodine, as outlined in Scheme 72. The ring expansion of the cyclobutanol derived from P-indanone enol ether and acrylonitrile gave an a,P-unsaturated nitrile. 

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