Some reactions of phospholene derivatives.
thesisposted on 19.11.2015, 09:17 by David Glynn Smith
A review of the chemistry of phospholene oxides is presented. The synthesis of 2,3-epoxyphospholane oxides is described, and the reactions of these compounds with Lewis acids were investigated. Four different attempts at forming the episulphide of 3-methyl-1- -phenyl-2-phospholene-l-oxide are reported, all of which were unsuccessful. The stereospecific synthesis of 3,4-epoxyphospholane oxides is discussed in terms of a directive effect from the phosphoryl group. The rearrangement of these epoxides with boron trifluoride etherate, to give vinyl ethers and phospholan-3-ones, was studied. Following a discussion of the alkaline hydrolysis of phosphonium salts, the hydrolyses of 1-methyl-1-phenyl-2- and 3-phospholenium iodides are described. The hydrolyses of 1-iodomethyl- phospholenium iodides were also investigated and found to proceed, in the majority of cases studied, to give ring-opened products and the phospholene oxide. Only with 1-iodomethyl-l,2-diphenyl-2-phospholenium iodide, where the incipient carbanion is relatively more stable, was ring expansion found to occur. Ring expansion of phospholenes was achieved using ethyl propiolate and dimethyl acetylenedicarboxylate. The hydrolysis of the products formed from phospholenes and acyl and aroyl chlorides is discussed in terms of nucleophilic attack either at phosphorus or at the carbonyl group, the former being favoured when substituted benzoyl chlorides are used (giving aldehydes), but the latter being favoured in the case of acyl chlorides to produce phospholenes and carboxylic acids. Ring expansion was found to occur when the product from benzoyl chloride and 1,2-diphenyl-2-phospholene was hydrolysed. Attempts to synthesise an epoxide of a cyclic unsaturated phosphonate are described. The breakdown in the mass spectrometer of 3,5,5-trimethyl-l,2-oxaphosphol-2-ene derivatives to give a metaphosphate analogue is discussed, and possible syntheses of the neutral compound are suggested. The hydrolyses of the methyl and phenyl esters derived from the 3,5,5-trimethyl-1,2-oxaphospholane system were studied. In all cases the ring-retained product with loss of the exocyclic ester group was isolated in greater than 60% yield. The mechanistic possibilities of this reaction are discussed. A short account of the synthesis of possible anti-inflammatory agents based on the acenaphthene system is presented in an appendix.