Photochemical fragmentation of the 2-phosphabicyclo[2.2.2]octa-5,7-diene ring system as a versatile method for generating 3-coordinate methylene phosphine oxides and sulfides

✍ Scribed by Louis D. Quin; Jian-Sheng Tang; Gyöngyi S. Quin; György Keglevich

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 695 KB
• Volume: 4
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/hc.520040212

✦ Synopsis

1,6-Dihydrophosphinine I -oxides with 4-chloro-3(or 5)-methyl substituents give cycloadducts with dimethyl acetylenedicarboxylate having the 2-phosphabicyclo[2.2.2]octa!-5,7-diene ring system that can be fragmented easily on irradiation with ultraviolet light (254 nm). The phosphorus-containing bridge is released as a derivative of the 3-coordinate methylene phosphine oxide species, R-P(0)=CH2. This species is too reactive to observe but is readily trapped by an addition reaction with alcohols to give phosphinates ( R = alkyl or aryl) or phosphonates ( R = 0-alkyl). These experiments constitute the first demonstration of the existence of RO-P(0)=CH2. Phosphoryl oxygen in the cycloadducts has been replaced by sulfur, and these sulfide5: fragment smoothly on irradiation. The 3-coordinate species Ph-P(S)=CH2 has been generated by other workers, but the species RO-P(S)=CH2 was generated here for the first time. The power of the bicyclic fragmentation route for the gen-Dedicated to Prof. .lames Cullen Martin on the occasion of his *To whom correspondence should be addressed. **Visiting Scientist from Nankai University, Tianjin, Peo-sixty-fifth birthday. ple's Republic of China.

eration of a variety of 3-coordinate P-methylene derivatives is made evident by this study.