Preparation and Reactions of 1,3-Diphosphacyclobutane-2,4-diyls That Feature an Amino Substituent and/or a Carbonyl Group
✍ Scribed by Hiroki Sugiyama; Shigekazu Ito; Masaaki Yoshifuji
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 213 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
The preparation and properties of a 1‐amino‐1,3‐diphosphacyclobutane‐2,4‐diyl and a 1‐benzoyl‐1,3‐diphosphacyclobutane‐2,4‐diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1‐diisopropylamino‐3‐methyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (7), which is formed by reaction of Mes*CP (4; Mes*=2,4,6‐t__Bu~3~C~6~H~2~) with lithium diisopropylamide and iodomethane, resulted in ring‐opening of the 1,3‐diphosphacyclobutane‐2,4‐diyl skeleton, as well as de‐aromatization of one of the Mes* rings. 3‐Oxo‐1,3‐diphosphapropene 8 and 7‐phosphabicyclo[4.2.0]octa‐1(8),2,4‐triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3‐oxo‐1,3‐diphospha‐1,4‐diene 10. 1‐Benzoyl‐3‐tert‐butyl‐2,4‐bis(2,4,6‐tri‐tert__‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (12) was isolated and characterized from the reaction of 4 with tert‐butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring‐expansion to afford 1‐oxo‐1__H__‐[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2__H__‐[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3‐diphosphacyclobutane‐2,4‐diyl intermediate 14. Thermolysis of 15 afforded 1‐oxo‐1__H__‐[1,3]diphosphole 16 in an Arbuzov‐type rearrangement.