Phosphoric acid 1.3.2- dioxaphospholanes

Cyclic Esters of Phosphorous Acid.—A large number of 2-substituted-4-methyl-l,3,2-dioxaphospholans (88) have been prepared and their stereochemistry and conformations investigated by 1H and 31P n.m.r.69 Unlike the corresponding 1,3-dioxans, the tra/w-isomer (88a) is favoured in all cases, and each isomer is best described in terms of two rapidly equilibrating half-chair conformers with the 4-alkyl group pseudo-axial or pseudo-equatorial. 

The reaction of the aminophosphanes t-Bu2PNH2 and F2PNH2 results in the formation of hexafluoroacetoneimine and phosphoric acid derivatives with and without addition of HFA. With aminodifluorophosphane, the expected formation of a 1,3,2-dioxaphospholane (see Section III,A,4) has been observed (263). 

Reaction of bis-(2-chloroethyl) H-phosphonate with triethylamine produces a cyclic ester of p-chloroethyl phosphorous acid [288], The rate of this reaction is very low. It has been proposed that in the presence of triethylamine, bis-(2-chloroethyl) H-phosphonate isomerizes into bis-(2-chloroethyl) phosphite. The latter forms the corresponding 2-chloroethyl-l,3,2-dioxaphospholane, accompanied by hydrogen chloride elimination. 

Sodium cyanide Phosphoric acid monoesters from 2-alkoxy-2-oxo-l,3,2-dioxaphospholanes... 

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