engleski

A study of reactions of sulphur containing dipolarophiles with 1, 3-dipoles

Several different methods for the synthesis of vinyl sulfoximines and sulfoxides have been investigated, and the products obtained have been investigated as dipolarophiles in 1, 3-dipolar cycloadditions with nitrile imines and nitrile oxides. Also, a new method for the preparation of an allylic sulfoximine has been found, and S-((E)-(3-ethoxycarbonyl) prop-2-enyl)-S-phenyl-N-(p-tolylsulfonyl)sulfoximine (142) showed high reactivity in the cycloadditions with benzonitrile oxide and diphenylnitrilimine. The cycloadducts were obtained as mixtures of regio- and diastereoisomers with moderate diastereoselectivity demonstrated only in the reaction with benzonitrile oxide. New β -Dimethylamino vinyl sulfoximine and sulfone were efficiently prepared by heating S-methyl-S-phenyl-N-(p-tolylsulfonyl)sulfoximine and methyl phenyl sulfone with DMF-dimethyl acetal. In the case of (E)-1-dimethylamino-2-phenylsulfonylethylene, the presence of the β -dimethylamino group completely reversed the regioselectivity of the cycloaddition with nitrile oxides compared to phenyl vinyl sulfone, and concomitant elimination of dimethyl amine gave rise to 3, 4-disubstituted isoxazoles. Benzo[b]thiophene-1, 1-dioxide showed very good reactivity and high regioselectivity in the cycloadditions with nitrile imines giving pyrazolines. Only one regioisomer was also isolated from the reaction with azomethine ylides derived from aziridines. In contrast, the reaction with the non-stabilised azomethine ylide, generated from sarcosine and benzaldehyde afforded cycloadducts as a mixture of regio- and steroisomers. The structure of one of the cycloadducts was determined by X-ray crystallography. The previously unknown N-[1λ 4-benzo[b]thiophenylidene]-4-methylbenzene sulfonamide was prepared by reaction of benzo[b]thiophene with [N-(p-toluenesulfonyl)imino]phenyliodinane. The reaction with Chloramine-T however was quite different and an unusual ring expanded benzothiazine was obtained instead of the expected sulfilimine. Its structure was determined by X-ray crystallography.

1; 3-Dipolar cycloaddition reactions; Benzo[b]thiophene 1; 1-dioxide; Sulfoximines; Sulfoxides; Sulfones; Nitrilimines; Nitrile oxides; Azomethine ylides; Regio- and stereoselectivity

nije evidentirano