New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid

Abstract

Various cyclic phosphonium structures are formed in high yield by the deprotection of unstable phosphine-aldehydes in acidic solution. When there is a methylene spacer between the phosphine and the aldehyde, a phosphonium ion [PHR 2CH 2CH(OEt) 2]Br 2, R=iPrOH, Et is obtained. Reaction of these phosphonium salts with water produces the dimers [–PR 2CH 2CH(OH)–] 2[Br] 2 R = iPr, Et. When there is an ethylene spacer as in PPh 2CH 2CH 2CH(OCH 2CH 2O), a remarkable tetramer with a 16-membered ring [–PPh 2CH 2CH 2CH (OH)–] 4[Cl] 4 forms as one diastereomer in hydrochloric acid solution. Reaction of HCl with the protected phosphine-aldehyde with a propylene spacer (PPh 2CH 2CH 2CH 2CH(OCH 2CH 2O)) results in the formation of the monomeric phosphonium salt [–PPh 2 CH 2CH 2CH 2CH(OH)–]Cl with a 5-membered ring. Solid state structures of different ring types were determined using X-ray diffraction experiment.