Phosphinoyl groups

It is well known that aziridination with allylic ylides is difficult, due to the low reactivity of imines - relative to carbonyl compounds - towards ylide attack, although imines do react with highly reactive sulfur ylides such as Me2S+-CH2-. Dai and coworkers found aziridination with allylic ylides to be possible when the activated imines 22 were treated with allylic sulfonium salts 23 under phase-transfer conditions (Scheme 2.8) [15]. Although the stereoselectivities of the reaction were low, this was the first example of efficient preparation of vinylaziridines by an ylide route. Similar results were obtained with use of arsonium or telluronium salts [16]. The stereoselectivity of aziridination was improved by use of imines activated by a phosphinoyl group [17]. The same group also reported a catalytic sulfonium ylide-mediated aziridination to produce (2-phenylvinyl)aziridines, by treatment of arylsulfonylimines with cinnamyl bromide in the presence of solid K2C03 and catalytic dimethyl sulfide in MeCN [18]. Recently, the synthesis of 3-alkyl-2-vinyl-aziridines by extension of Dai s work was reported [19]. 

The [l,2]-a rearrangement of phosphinothioates into (alkylsulfanyl-methyl)phosphine oxides using a chiral phosphinoyl group has also been reported (see Sect. 5.1.1.). 

The equilibrium constant for the ring inversion of 2-(diphenylphosphinoyl)tetrahydrothiopyran has been measured from the integration of the 31P signals in TFlF-<78 at temperatures below the coalescence temperature (531P at room temperature is 30.02). At 183 K the equilibrium constant (K) was calculated to be 0.20 with AG° 183 k =+0.59 kcal mol. The difference in chemical shift between the signal for axial and equatorial diphenyl-phosphinoyl groups in 215 and 216 was 1.8 ppm <1998T1375>. 

Thus bond formation is 37% of its full potential and bond fission has proceeded to 63%. There is thus an imbalance in bond formation which is reflected by the phosphinoyl group s becoming more positive than in its reactant or product state (Scheme 36). 

The involvement of ketoses in the Abramov and related reactions gives rise to linear phosphonic acids in which the phosphinoyl group is sited on a carbon atom other than at position C(i). The dimethyl phosphite ester 327, derived from 1,3-di-O-benzyl-o-... 

Dimethyl [a-(hydroxyimino)benzyl]phosphonate is stable in mineral acid but decomposes in formic acid containing formate with the liberation of benzonitrile, but otherwise the behaviour is different from that in boiling acetic acid when an additional product, a phosphoramidate ester, is obtained by a Beckmann rearrangement. For the oximes of the (4-methoxybenzoyl)- or (4-chlorobenzoyl)-phosphonic esters, only the phosphoramidate diester 127 is obtained, but for all the substrates examined [additionally the unsubstituted benzoyl- as well as the (4-methylbenzoyl)phosphonic derivatives], the formation of the phosphoramidate ester demonstrates a high migratory aptitude of the phosphinoyl group (Scheme 22) ... 

The sulfinyl- and sulfonyl-substituted dioxanes were obtained as a mixture of two stereoisomers. The C-3 hydroxyl group of the major stereoisomer was axially oriented, and the sulfinyl, sulfonyl, and phosphinoyl groups at the C-4 position were placed equatorially, based on the and NMR spectra [84]. 

P ligand first by adding one C-NH bond in a reductive amination process, and then forming the second C=N bond and finally the third-generation complex 14 (Fig. 40). This new class of catalyst was effective in the rapid reduction of N-diphenylphosphinoyl-activated imines containing phosphinoyl groups in >99 % e.e. (Fig. 41) [126, 127]. 

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