Non-aromatic Boron Heterocyclics

Non-aromatic Boron Heterocyclics.—The range of cyclic dialkoxyboranes derived from monosaccharides has been extended to cover deoxyaldohexoses [by treatment of the sugar with ethyl(dimethoxy)borane] and derivatives of glucose (by a novel reduction process). If two dioxaborolane units are appropriately disposed in space, exchange of alkoxy groups between boron atoms is possible, as for example in the equilibration of compounds (17) and (18).  

2-dioxaborolane is amongst the products from the photochemical reaction of ethyl 3-(dicyclohexylboryl)acrylate in alcoholic medium. Some 1,3,2-dioxaboracycloalkanes undergo equilibration between oligomers of different 

Tokuda, V. V. Chung, and M. Itoh, Hokkaido Daigaku Kogakubu Kenkyu Hokuku, 1980, 37 (Chem. Abstr. 1980, 93, 104 734). 

A number of novel l-aza-2-bora-3-oxacyclopentanes such as (19) have been prepared. Compound (20) is the first monomeric pyrazolylborane containing trigonal boron. Preparation of compounds (21) by reaction of RBHa with carbonyldihydrazine has been reported.  

The effect of angle strain on the hybridization of boron is illustrated by compounds ranging in structure from (22) through (23). The smallest member of the series, (22), is a tight dimer under all conditions measured, but (23) has a stable, planar BN3 arrangement.  

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