SPIROSULFURANES WITH DIFFERENT HETEROATOMS IN AXIAL POSITIONS - A COMPARISON OF N-S(IV)-O AND N-S+(IV)...O = BOND SYSTEMS

Three novel spirosulfuranes with N and O heteroatoms in axial position s and with five- and six-membered spirorings (4-6), as well as the mol ecular complex of the dipolar ion 7 with methanol, have been prepared and their molecular structures determined by X-ray diffraction. The mo lecular structures of the spirosulfuranes 4 6 show slightly distorted geometries, while that of the dipolar ion 7 is considerably distorted about the central sulfur. The axial interatomic distances for S N and S-0 in 4-6 range from 1.71 to 1.74 angstrom and from 2.13 to 2.25 angs trom, respectively (1.69 and 2.60 angstrom for 7). The axial N-S-O and the equatorial C(ar)-S-C(ar) angles lie in the intervals 174-179-degr ees and 104-105-degrees, respectively, for the spirosulfuranes 4-6 (15 7 and 104-degrees for 7). The S-Ca, bond lengths in all of the compoun ds investigated are similar to those given for typical S(IV) C(ar) bon ds (1.76 1.82 angstrom). A comparison is also presented between the st ructural parameters of the spirosulfuranes 4 6 and those of the cyclic sulfonium salts 1a-3 and of the molecular complex 7 with analogous st ructures to the spirosulfuranes studied. The conformations for all of the model compounds as well as for the sulfoxide 8 and sulfide 9 relat ed to the spirosulfuranes and sulfonium salts investigated are also di scussed.