Inapplicability of the Antiperiplanar Lone Pair Hypothesis to C-P Bond Breaking and Formation in Some S-C-P(+) Systems

Piotr P. Graczyk; Marian Mikolajczyk

doi:10.1021/jo941771m

Inapplicability of the Antiperiplanar Lone Pair Hypothesis to C-P Bond Breaking and Formation in Some S-C-P(+) Systems

J Org Chem. 1996 May 3;61(9):2995-3002. doi: 10.1021/jo941771m.

Authors

Piotr P. Graczyk¹, Marian Mikolajczyk

Affiliation

¹ Center of Molecular and Macromolecular Studies, Polish Academy of Science, Department of Organic Sulfur Compounds, Lodz, Sienkiewicza 112, PL-90-363, Poland.

PMID: 11667160
DOI: 10.1021/jo941771m

Abstract

Both C(2)-P bond breaking and formation in the S-C-P(+) system do not occur according to the antiperiplanar lone pair hypothesis. Experiments using 2-phosphonio derivatives of 5-tert-butyl-1,3-dithiane and cis-4,6-dimethyl-1,3-dithiane are against the participation of higher-energy boat conformers as reactive intermediates. The results obtained support a possibility of conformational adjustment in the course of the reaction. Stereoelectronic control of the C(2)-P bond breaking and formation results from interplay of several factors. The role of the n(S)-sigma(C(2))(-)(P) and sigma(C(4,6))(-)(S)-sigma(C(2))(-)(P) hyperconjugation, as well as of the repulsive interactions between lone electron pairs pi(S) of endocyclic sulfur atoms and pi-electrons of the phenyl ring(s) connected with phosphorus, is discussed.