Bruno Radatus

Cyclopropylcarbinyl–oxocarbonium ions. Part VII. Orientational effects

The anomeric 2,3-dideoxy-2,3-C-methylene-D-allopyranosides (2α and β) along the with homoallyl iodide (6) comprise a configurationally related cyclopropylcarbinyl–system; the 2,3-dideoxy-2,3-C-methylene-D-mannopyranosides (7α and β) along with the homoallyl iodide (11) comprise a second, different system. The three members of each system should undergo solvolysis through a common, highly stabilised cyclopropylcarbinyl–oxocarbonium ion [(3) or (8), respectively]. Evidence in support of this is the fact that compounds (2α and β) and (6) are hydrolysed to the same δ-hydroxy-cyclopropanecarbaldehyde (5), presumably formed via the related, cyclic hemiacetal (4). A study of the solvolysis of the cyclopropyl compounds (2α and β) and (7α and β) indicates that orientational effects are not important; however, in the case of the homoallyl iodides (6) and (11) an effect is observed.

4,6-O-benzylidene-3-deoxy-3-C-(iodomethyl)-D-glucal(4,6-O-benzylidene-1,2,3-trideoxy-3-C-iodomethyl-D-arabino-hex-1-enopyranose)

The transformation of 4,6-O-benzylidene-3-deoxy-3-C-(iodomethyl)-D-allal (3) into the epimeric D-arabino-derivative, the title compound (5), is described.