Some asymmetric organotin compounds.

Attempts have been made to prepare and resolve asymmetric organotin compounds for use in studies of the mechanism of substitution reactions at tin. The stages in the attempted resolutions were the synthesis of the asymmetric tin compound, the introduction of a functional group and resolving agent, the separation of the diastereoisomers, and the recovery of the resolved tin compound. Reviews are therefore given of the methods which have been used for the preparation of unsymmetrical organotin compounds, for the introduction of functional groups into organotin compounds, and of the methods which have been used to resolve compounds of other group IVB elements. Several unsuccessful attempts were made to repeat the only previously reported resolution of an organotin compound (ethylmethyl-n-propyltin iodide) and reasons for the failure to do so are suggested. The attempted resolution of ethylmethyl-n-propyl-p-trimethyl- ammonophenyltin iodide (with silver (+)-camphor-ss-sulphonate) and of 3-aminopropylethylmethylphenyltin (with d-tartaric acid) resulted in cleavage of the tin-aryl bond. As a part of this work the reported deamination of primary amines with triphenyltin hydride was re-examined and it was shown that instead of deamination a catalytic decomposition of triphenyltin hydride to hexaphenylditin and hydrogen takes place. Samples of [2-carb-(-)-menthoxyethyl] methyl-1-naphthylphenyltin, with specific rotations of -33.7 and -18.3°, were prepared but an optically active organotin compound, free from the resolving agent, could not be isolated. The attempts at separating the diastereoisomers of s-butylethyl- methylphenyltin and of [2-carb-(-)-menthoxyethyl] ethylmethyl-n-propyltin by vapour-phase chromatography and of 1-naphthylmethylphenyltin (-)-menthoxide by fractional crystallization were unsuccessful.