Reaction of p-Nitrobenzenesulfonyl Azide with Alkylidenecycloalkanes

Article abstract of DOI:10.1021/jo00315a023

The 1,3-dipolar addition of p-nitrobenzenesulfonyl azide (PNBSA) to alkylidenecycloalkanes 1-3 was studied, and the products of hydrolysis were isolated and identified.The products from 1 and 2 suggest that these alkenes react to give a single triazoline intermediate.The tetrasubstituted derivatives 3, however, give both possible reaction modes.The products initially derived from 3 were the two sulfonimides expected from ring expansion (4, R=R'=Me) and methyl migration (5).Upon hydrolysis, the respective ketones, 8 and 9, were obtained in excellent overall yields.The ring-expanded sulfonimides 4 (R=R'=Me, n=6-8) were found to be less reactive under hydrolytic conditions than their respective isomers 5.Thus, subjecting the PNBSA adducts to mild hydrolysis conditions allowed the isolation of pure 9 (n=6-8).Also, in two cases (i.e., n=7,8), the pure imides 4 (R=R'=Me, n=7,8) crystallized from the hydrolysis solutions.Dipolar cycloaddition of p-nitrobenzenesulfonyl azide to 2-isopropylidenebicyclo<2.2.1>heptane followed by acid hydrolysis gives endo-2-acetyl-exo-2-methylbicyclo<2.2.1>heptane (4.1 percent), exo-2-acetyl-endo-2-methylbicyclo<2.2.1>heptane (16.3 percent), 2,2-dimethylbicyclo<3.2.1>octan-3-one (2.1 percent), and 3,3-dimethylbicyclo<3.2.1>octan-2-one (36.8 percent), thus providing evidence that electronic factors are much more important than steric effects in controlling regioselectivity.