The work described in the thesis has two objectives. The first is to prepare P(V) compounds, mainly phosphine sulfides, which have one or more P-chiral phosphorus atoms which are also attached to another heteroatom such as nitrogen. The second objective is to examine the effectiveness of these compounds as catalytic ligands in the borane reduction of ketones, and the addition of diethylzinc to carbonyl compounds. Secondary phosphine oxides and sulfides also containing P-chiral phosphorus atoms, and which are used to prepare the above phosphine sulfides, are also evaluated as ligands in the asymmetric reactions. _{p p}...[ Read more ]

The work described in the thesis has two objectives. The first is to prepare P(V) compounds, mainly phosphine sulfides, which have one or more P-chiral phosphorus atoms which are also attached to another heteroatom such as nitrogen. The second objective is to examine the effectiveness of these compounds as catalytic ligands in the borane reduction of ketones, and the addition of diethylzinc to carbonyl compounds. Secondary phosphine oxides and sulfides also containing P-chiral phosphorus atoms, and which are used to prepare the above phosphine sulfides, are also evaluated as ligands in the asymmetric reactions.

Racemic tert-butylphenylphosphinothioic acid 1 was resolved to provide both the (R_p)- and (S_p)-phosphinothioic acids 1. Each was converted into the corresponding chloridates 26 by reaction with oxalyl chloride, or into the bromidates 126 by reaction with oxalyl bromide. The structure of the product was confirmed by an X-ray crystallographic study. Treatment of the chloridates with n- or tert-butyllithium in THF and quenching with methanol gave secondary phosphine sulfides 46. It was established by means of X-ray crystallography that the reaction proceeded with retention of configuration.

By reaction with ammonia, indole, and the aliphatic diamines ethylenediamine and propylene diamine, the chloridates were converted into the crystalline thionophosphinoamidates 127 and 128, and the crystalline diamidates 129 and 130. Reaction with (1S,2S)-(+)-1,2-diaminocyclohexane was much more sluggish, and only (R_p)-chloridate 26 reacted with it to give the bisthionophosphinodiamidate 131 in low yield. The tris-thionophosphinotriamidate 132 was obtained in good yield from tris-(2-aminoethyl)amine and the chloridate 26.

In the borane reduction of acetophenone with borane-THF complex, reactions with the secondary (R_p)-phosphine oxide 2 were initially examined, but it was found that 1-butanol was a substantial by-product. In the addition of diethylzinc to aromatic aldehydes, in the presence of the secondary (R_p)-phosphine oxide 2, and the thionophosphoroamidates 127-130 over 60% enantiomer excess was obtained, with the (R_p,R,_p)-diamidate 129 derived from ethylene diamine being the best ligand. Thus, the optimum ligands are structurally very distinct to other ligands so far used in this intensively-studied reaction.