The mechanism of the hydrolysis of ethylenephosphates has been reviewed critically. It was pointed out that 1) the direct evidence for the formation of the pentacoordinate intermediate is necessary to establish the Westheimer's mechanism 2) the Westheimer's mechanism may not always applicable to the hydrolysis of five-membered cyclic phosphates. From this point of view, the hydrolysis of hetero atom substituted ethylenephosphates and vinylenephosphates have been reviewed and the following two extreme mechanisms were suggested to operate in the hydrolysis of five-membered cyclic phosphate analogs. 1) Associative pentacoordinate intermediate mechanism with the exclusive formation of the ring retention product. 2) Direct displacement mechanism with the exclusive formation of the ring cleavage product. Furthermore, a novel phosphorylation method of alcohols using the ring strain of vinylenephosphates analogs was introduced.
The theory of bicycloaromaticity has been discussed according to Goldstein-Hoffmann's formulation of “ribbon mode”. Its theoretical consequence has stimulated synthetic efforts toward the stabilized longicyclic (CH) n anion series-the bicyclo [3. 2. 2] nonatrienyl, the bicyclo [3. 3. 2] decatrienyl, the barbaralyl and the bicyclo [4. 3. 2] undecatetraenyl anions. Recent studies of these anions are discussed with regard to their thermodynamic stability, chemical reactivity and thermal rearrangement.
The newer preparative methods for the aromatic fluorine compounds were reviewed. The direct fluorination, indirect fluorination using xenon difluoride and trifluoromethyl hypofluorite, and the Cl-F and NO2-F exchange reactions were included.