An ab initio CBS-QB3 quantum chemical study of singlet and triplet sulfonylnitrenes insertion into acetylenes and nitriles

摘要

The reactions of methylsulfonylnitrene 1a and trifluoromethylsulfonylnitrene 1b with acetylene 2, dimethylacetylene 3, acetylenedicarboxylic acid 4, hydrogen cyanide 5, acetonitrile 6, cyanoformic acid 7 were studied theoretically at the CBS-QB3 level of theory. The main products of the reaction of triplet sulfonylnitrenes (3)1 with alkynes 2-4 are 1,2,3-oxathiazole 2-oxides 10 formed from triplet diradical adducts after intersystem crossing (ISC) to their singlet spin-isomers. Products 10 are also formed from singlet nitrenes (1)1 along with N-vinylidenesulfonamides 9 and 1-(alkylsulfonyl)-1H-azirines 11. The latter, being antiaromatic, isomerize exothermically to 2-(alkylsulfonyl)-2H-azirines 12. In a similar way, both singlet and triplet sulfonylnitrenes 1 react with nitrites 5-7 to give 1-(alkylsulfonyl)-1H-diazirines 16. With singlet nitrenes, nitrites 5-7 can also react with the formation of 2-(methylidyne)-1-(alkylsulfonyl)diazan-2-ium-1-ides 14, which undergo either intramolecular 1,3-cyclization to 3-(alkylsulfonyl)-3H-diazirines 17 or intramolecular 1,5-cyclization to 1,2,3,4-oxathiadiazole 2-oxides 15. Relative stability of the key products and activation barriers of their interconversion are discussed. (C) 2018 Elsevier B.V. All rights reserved.