Imines with phosphoranes

D. Miscellaneous.—Low yields of the spirophosphoranes (34) were obtained on heating the phosphorane (32) with the aziridines (33). Stable phosphoranes have been obtained from phenanthraquinone mono-imine (35) and trialkyl phosphites, and from 2-chlorotropone (36) and ylides. In the latter reaction cyanomethylenetriphenylphosphorane gave instead the betaine (37). 

Diphenylcarbodi-imide reacts with ylides to give, in general, the iminophosphorane (86) and the imines (85). The latter usually react with a second mole of ylide to give the stable phosphoranes (87) although the imine (85 R = R = Ph) was isolated. Hydrolysis of the solution... 

With X = HNPPr3 the new phosphorane imine complex (326a) was obtained. Spectroscopic and structural data indicate that the HNPPr3 ligand favors an ylidic structure.854... 

Finally, a reaction should be mentioned in which a nucleophile gives support to another reacting species without appearing in the final product. Diphenyl cyclopropenone interacts with 2,6-dimethyl phenyl isocyanide only in the presence of tri-phenylphosphine with expansion of the three-ring to the imine 344 of cyclobutene-dione-1,2229,230 Addition of the isocyanide is preceded by formation of the ketene phosphorane 343, which can be isolated in pure formss 231 it is decomposed by methanol to triphenyl phosphine and the ester 52. 

Alternatively, phosphine imines 266 were treated with various phenylacetyl chlorides 270 (method B). Surprisingly, phosphonium salts 271 were isolated with 25 to 97% yield, which could be deprotonated by means of a base to build up the corresponding phosphoranes 272 (66-89% yield). Upon heating to... 

Phosphorane (64) can be isolated in pure form when diphenylcyclopropenone is treated with triphenylphosphine. This product arises, at least formally, by interception of the ring-opened species 49 by the phosphine. It can be decomposed by methanol to methyl a-phenylcinnamate and triphenylphosphine. Isocyanides such as 2,6-dimethylphenyl isocyanide react with 64 to yield the interesting product 65, an imine of cyclobutenedione (equation 60). ... 

Reaction of the nitrile-imine 42 with the phosphonite 43 gave the bicyclic phosphorane 46 via intermediates 44 and 45. The structure of 46 was confirmed by elemental analysis, IR, H/ P nmr and finally X-ray crystallography which revealed that the bicyclic structure was almost planar. ... 

The formation of acrylonitriles from the reaction of dihalogenomethylene-phosphoranes with aroyl cyanides has now been extended to include the use of aliphatic acyl cyanides, although the conditions need to be closely defined. Perfluoroisocyanates with diphenylmethylenetriphenylphosphorane give the expected keten-imines (28) or their rearrangement products (29). Formylation of both reactive and stable ylides has been achieved using the mixed anhydride of formic and acetic acids. ... 

A further investigation of these oxidative addition reactions revealed a complete redistribution of ligands between (69) and (70) involving a series of observable phosphoranes (71), (73), (75) and (76) containing P-H bonds (Scheme 1) 25. Monocyclic phosphoranes with P-H bonds have also been shown to add to activated carbon-carbon and carbon-nitrogen double bonds to form new phosphoranes containing P-C bonds. For example (78) reacts with acrylonitrile (79) or the imine (80) to give (81) and (82) respectively. 

Phosphoranylideneaminoquinones, e.g. (20), have been prepared in good to excellent yields by the reaction of phosphines with [2,l]benzisoxazole-4,7-quinones, e.g. (19)." A safer alternative to the vinyl azide-based synthesis of (N-vinylimino)phosphoranes (21) has been reported (Scheme 1)." N-(AlkyIthiomethyl)iminophosphoranes (23) have been synthesised from the benzotriazole-substituted iminophosphorane (22) and used without isolation to provide routes to N-alkylthiomethyl-imines, -amides, and -ureas. Tetraazolyl-substituted ylides (25) and (26) are the products of the reaction of vinylphosphonium salts (24) with excess sodium azide." The novel 1,2-1 -azaphosphete (28), which is potentially antiaromatic, has been prepared by the reaction of the azide... 

Three variations of this methodology lead to different heterocyclic products. Use of the mono-oxime 115 results in formation of the benzoxazole 116 after elimination of methanol (equation (14)) (89T4585). Use of two moles of ]V-phenyliminophosphorane (PhN - PPhs) gives the 2,3-dihydro-l,2,3-benzoxadiazole 117 (40%) (equation (15)), presumably after initial formation of the quinone imine (02SC2779). Reaction with phosphanylidene phosphoranes (ArP - PMes) gives 1 2-benzodioxophospholanes 118 (equation (16)) (04CC146). 

Trimethyl aluminium will react with methylene trimethyl phosphorane to form a crystalline zwitterionic compound, mp = 62°C (9.148). With triphenyl or trialkyl phosphine imines in the presence of ether the products contain rings of aluminium and nitrogen (9.149). 

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