The synthesis and properties of some 2-phenyl-l.3.2-oxazaborolans are described and the i.r. spectra and general mass-spectral features of these compounds are discussed.RECENTLY there has been renewed interest in the synthesis and properties of heterocyclic organoboranes. For example the 2-substituted 1,3,2-diazaboracycloalkanes have been reviewed2 and work concerning the dioxa-and dithia-borolans and borinans has been publisl~ed.~ iVe have been interested in heterocyclic organoboranes for some time4-7 and were surprised to find that with few exceptions the 1,3,2-0xazaborolans appear to have been ignored. We therefore report our results concerning the preparation and properties of these compounds.
RESULTS AND DISCUSSIONTwo general methods were used for the synthesis of the 2-phenyl-l,3,2-oxazaborolans : (a) reaction of an aminoakohol with bis(et1iylthio)phenylborane ; and (b) reaction of an aminoalcohol with bis(diethy1amino)phenylborane. In both cases, one of the products of the reaction is volatile and this leads t o a very smooth synthesis of the boron heterocycles. For example 5methyl-2-phenyl-l,3,2-oxazaborolan was obtained from the interaction of 1-methyl-2-aminoethanol and bis-(ethy1thio)phenylborane in benzene solution [equation (l)]. The reaction was stopped when the volatile products passed into an aqueous lead(I1) acetate solution HO-CHMe /O-CHMe B(SEt)ZPh + I -PhB, I t 2EtSH ( 1 ) H2N-CH2 N-CH2 H failed to give any precipitation of lead(r1) hydrogensulphide. I n a similar way the interaction of bis-(diethy1amino)phenylborarie and 2-amino-2-methylpropanol gave 4,4-dimet hyl-2-phenyl-l,3,2-oxazaborolan H2N-CMe2 ,N-CMe2 H E(NEt,I,Ph + I -PhB I t 2Et2NH ( 2 ) HO-CH2 ' 0 -CH2[equation ( 2)]. Using method (a), nine 2-phenyl-l,3,2oxazaborolans were prepared. Also 2-phenyl-l,3,2oxazaborinan was prepared to enable us to compare the properties of the five-and six-membered heterocyclic systems. The physical properties and analytical data for these compounds are given in the Table.The 2-phenyl-l,3,2-oxazaborolans were all obtained as distillable liquids ; compounds (VI) and (VII) solidified on standing. Attempts to prepare 2-alkylthio-l,3,2-
