Computational study of singlet and triplet sulfonylnitrenes insertion into the C-C or C-H bonds of ethylene

摘要

Formation of N-sulfonylaziridines, N-ethylidenesulfonamides, N-vinylsulfonamides and 4,5-dihydro-1,2,3-oxathiazole 2-oxides by the reaction of singlet and triplet trifluoromethyl-, methyl-and tosylnitrenes with ethylene is studied computationally at the B3LYP/6-311++G(d,p) level of theory in both gas phase and in solution. Singlet sulfonylnitrenes react with ethylene via [1 + 2]-cycloaddition exothermically to give N-sulfonylaziridines. Triplet sulfonylnitrenes are formed from the singlet ones by the intersystem crossing with the energy barrier not exceeding 2.5 kcal/mol and react in a stepwise fashion by C-addition or H-abstraction. The C-addition gives rise to the formation of N-sulfonylaziridines or N-ethylidenesulfonamides depending on the S-N-C_(sp)3-C_(sp)2 dihedral angle, with the barrier to rotation about the N-C_(sp)3 bond not exceeding 2.5 kcal/mol. The H-abstraction results in N-vinylsulfonamides. Transformation of N-sulfonylaziridines to N-ethylidenesulfonamides requires to overcome the barrier of 57-60 kcal/mol, N-ethylidenesulfonamides to 4,5-dihydro-1,2,3-oxathiazole 2-oxides-74-80 kcal/mol and N-vinylsulfonamides to N-ethylidenesulfonamides-about 64 kcal/mol. The use of the polarizable continuum model does not lead to a change of the course of the reaction of trifluoromethanesulfonylnitrene with ethylene and only slightly affects the relative energies of the products, intermediates and transition states.