Transannular sulfur—nitrogen interaction in 1,5-thiazonine derivatives: an X-ray study
摘要:
A sulfoxide-lactam (2) and sulfide-N-acetyllactam (3), each with a nine-membered, boat-like 1,5-thiazonine ring, have been prepared and their molecular structures determined by X-ray diffraction. Only compound 2, with a trans-amide structure, exhibits sulfur-nitrogen close contact with a sulfurane-like trigonal bipyramidal geometry about sulfur (r(S ... N) = 2.780(1)angstrom; theta(O=S ... N) = 171.0(1)-degrees). The interatomic distances r(S=O) = 1.501(1)angstrom and r(O=S ... N) = 4.281(1) angstrom are in agreement with the usual S=O double bond and S ... N close contact rather than with O-S-N hypervalent bonds. Owing to the bulky N-acetyl group, the amide part in the ring of compound 3 has a cis structure with sulfur and nitrogen atoms lying 4.045(2) angstrom apart.