G. N. Molchanova

Synthesis of carborane-containing phosphates by catalytic phosphorylation

The catalytic phosphorylation ofo-carboranylmethanol with different phosphorus acid chlorides has been studied. This method makes it possible to obtain esters of phosphorus acids and esters of the corresponding phosphorus acid chlorides containing carboranylmethyl groups. The catalytic phosphorylation of 1,2-bis(hydroxymethyl)-o-carborane affords both acyclic and cyclic phosphate esters. The structure of the synthesizedo-carborano[1,2-e]-1,3,2-dioxaphosphepane was confirmed by X-ray diffraction analysis.

Catalytic synthesis of phosphoryl isocyanates

A general efficient method for the synthesis of phosphoryl isocyanates was developed. The method involves reactions of phosphoryl chlorides with sodium cyanate in the presence of anhydrous magnesium chloride as a catalyst.

Silicon-induced diastereoselectivity of the catalyzed phosphorylation of 1-(perfluoroalkyl)-ω-(trialkylsilyl)alkan-1-ols

The stereochemistry of catalytic phosphorylation of 1-(perfluoroalkyl)-ω-(trialkylsilyl)alkan-1-ols with pentavalent phosphorus acid monochlorides (phosphonochloridates, methyl(phenyl)phosphinic chloride, and phosphorochloridates) was studied. The effects of the structures of alcohols and phosphorylating agents on the degree of the reaction diastereoselectivity were investigated. Methylphosphonochloridates were found to react most stereoselectively; the diastereoselectivity of the phosphorylation is independent of the donor or acceptor character of substituents at the phosphorus atom, being determined by their volumes. In the series of silylalkanols, the diastereoselectivity of the reaction the higher the closer the Si atom to the reactive site of the molecule, the larger the volume of the perfluoroalkyl substituent, and the more pronounced the electron-withdrawing properties of the substituents at the Si atom. A reaction mechanism is proposed that rationalizes the stereoselectivity of the reaction.

Synthesis and thermal stability of silicon-containing esters of phosphorus acids

A number of trialkylsilylmethyl diphenyl phosphates MeRR′SiCH2OP(O)(OPh)2 (1a-e: R=Et (a), Pr (b), CF3CH2CH2 (c, e), Me3SiCH2 (d); R′=Me (a-d), Et (e)) were synthesized and their thermal rearrangement, of the 1,2-shift type, was studied. The rearrangement consists of the migration of an alkyl group from Si atom to the methylene carbon atom and gives the corresponding silyl esters. The rate of the rearrangement was found to increase in the order1d<1b<1a<1 (R=R′=Me)<1c corresponding to the enhancement of the total inductive effect (−I) of the substituents at the Si atom. The relative migration ability of the substituents at the Si atom, determined by GC/MS analysis of the disiloxane fraction resulting from hydrolysis of pyrolyzed phosphates1a-e, increases in the order R=Pr<Et<CF3CH2CH2<Me≪Me3SiCH2, which differs substantially from the order in which the rate of the rearrangement of phosphates1a-d changes. The electronegativity of the migrating group affects noticeably the relative ability to migrate.

Catalytic phosphorylation of o-carboranylmethanol

In previous work [I], we showed that the phosphorylation of weakly nucleophilic polyfluoroalkanols, such as l,l-dihydroperfluoroalkanols, is catalyzed by several metals and their chlorides. We have found that such catalytic phosphorylation is also applicable for rather weakly nucleophilic o-carboranylmethanol (I). Thus, the corresponding chloride and ester derivatives are formed when POCI a and chlorophosphates are used as the phosphorylating agents in the presence of magnesium as the procatalyst upon heating for 0.5-3 h.

Synthesis of silicon-containing esters of phosphorus acids and study of their thermal stability. 3. Thermal rearrangement of triorganosilylmethyl esters of diphenyl phosphoric acid

Conclusions1.A method has been developed for the preparation of a series of triorganosilylmethyl esters of diphenylphosphoric acid.2.All the triorganosilylmethyl esters of diphenylphosphoric acid which were examined undergo thermal rearrangement involving the migration of a radical from the Si atom to the methylene C atom according to a 1,2-shift. The influence of the type of radical at the Si atom on the rate of the rearrangement has been studied.