Amide acetals spirocyclic

Spirocyclic triazolines are rare entities, however reduction of a-azidocycloalkyl-nitriles (or amides) affords spirocyclic triazolines in variable amounts. Azide (85a) afforded cyanoamine (86a) and spiro-l,2,3-triazole (87) in 56% and 16% yield, respectively. Similarly, azide (85b) afforded the spiro-l,2,3-triazolone (88) in 25% yield along with some starting material, some reduced linear triazine and the amine (86b). When 88 was thermolyzed in acetic acid, the a-acetoxyamide (89) was obtained [94JOC(59)6853]. 

Decomposition of a-diazo ketoamides 208 in the presence of substituted propiolic esters gives spirocyclic oxiranes 209. The reaction involves intramolecular addition of a rhodium carbenoid onto the oxygen atom of the amide group to yield the carbonyl ylide, which, after 1,4-H-migration, produces a cyclic ketene N,0-acetal 210. The latter further reacts with the activated triple bond of the dipolarophile to form a zwitterionic intermediate and, finally, a spirocycloadduct (Scheme 26) (90JA2037). 

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