C,C-Diacetylenic Phosphaalkenes as Heavy Diethynylethene Analogues

• DOI: 10.1021/jo901942u
• Publication Date: 2009-11-13T13:43:30Z
• Authors: Elisabet Öberg; Bernhard Schäfer; Xue-Li Geng; Jenny Pettersson; Qi Hu; Mikael Kritikos; Torben Rasmussen; Sascha Ott
• Keywords: 01 natural sciences; 0104 chemical sciences

A series of C,C-diacetylenic phosphaalkenes 1b-e has been prepared from 1-chloropenta-1,2-dien-4-ynes 6b-e in a reaction with Mes*PCl(2) (Mes* = 2,4,6-((t)Bu)(3)Ph) in the presence of LDA. Under identical conditions, isomeric butadiyne-substituted phosphaalkenes 2c-f can be obtained from 3-chloropenta-1,4-diynes 5c-f. The title compounds represent rare examples of diethynylethenes in which a constituting methylene has been replaced by a phosphorus center. The formation of both isomers can be rationalized by a common pathway that involves isomeric allenyllithium species. Spectroscopic, electrochemical, and theoretical investigations show that the phosphorus heteroatoms are an intrinsic part of the compounds' pi-systems and lead to decreased HOMO-LUMO gaps compared to those in all-carbon-based reference compounds.