Oxazaphosphorinanes

The XRD analysis of solid pentaoxyphosphorane 12 and the NMR study of its solution also point to an ae structure50. The same is true for the oxazaphosphorinane rings in 2 64,65,68 a twisted boat configuration60,68, and for the rings in the dithiaphos-... 

Anilino-benzyl)-3-isopropyl-l,3,2-oxazaphosphorinan-2-oxid 39% Schmp. 154—155°... 

Die Spaltung von 2-Alkylamino-l,3,2-oxazaphosphorinan-2-oxiden verlauft mit etheri-scher Chlorwasserstoff-Losung152 z.B. ... 

In Erganzung der Angaben im Bd. XII/2, S. 461—462, sei im folgenden die Synthese von 2-Amino-l,3,2-oxazaphosphorinan-2-oxiden erwahnt843 ... 

In gleicher Weise erhalt man 2-(4-Methoxy-anilino)- (44% Schmp. 180°) und 2-(4-Ethyl-anilino)-l,3,2-oxazaphosphorinan-2-oxid (37% Schmp. 177°). 

Oxazaphosphorinan 3-(2-Chlor-ethyi)-2-[(2-chlor-ethyl)-ethylamino]-4-hydroperoxid- -2-oxid E13/1, 575... 

Although the stereoselective formation of C-C bonds has been actively pursued in the last two decades, it was not until 1982 that the first stereoselective C — N bond formation was reported20, using the enantiomerically pure 1,3,2-oxazaphospholidine and 1,3,2-oxazaphosphorinane derivatives 1 and 2, respectively, as well as their enantiomers. Derivative 1 is easily accessible from (—)-ephedrine, phosphonis oxychloride and AUV-dimethyl hydroxylamine. A related route leads to 2. 

A high degree of asymmetric induction has been realized in the carbanion-accelerated Claisen rearrangement of phosphorus-stabilized anions. Treatment of 1,3,2-oxazaphosphorinane (166) with freshly prepared lithium dimsylate led to a 95 5 ratio of a-methyl ketones (167) and (168) (Scheme 33). Li coordination combined with steric interactions provide the necessary control elements for stabilization of the highly organized allyl anion conformation (169). 

A series of 2-alkyl-, 2-alkanoyl- and 2-aroyl-2-oxo-l,3,2-oxazaphos-phorinanes bearing N-benzyl, N-benzhydryl and N-trityl substituents (294) have been obtained and their conformational preferences in solid state analysed. All 2-alkanoyl- and 2-aroyl-2-oxo-l,3,2-oxazaphosphorinanes had a gauche or anti relationship between the P = O and C = O bonds. This is presumably to minimise dipolar interactions between the two bonds as observed in a-diketones. ... 

The diastereoselectivity in the alkylation of N-substituted 2-oxo-2-propyl-1,3,2-oxazaphosphorinanes (435) is influenced by the bulkiness of the nitrogen substituent. The ot-carbanion derivatives of (435) when R = CHPh2 and R = CPhs are unstable in the presence of DMPU and afford unexpected products (Figure 79). 

Hanessian and Beaudoin [310] have performed the diastereoselective condensation of lithiated phosphonamides 1.74 with prochiral or chiral cyclohexanones. Each enantiomer of the nonracemic alkene product is prepared from the appropriate reagent (Figure 6.34). Denmark and Chen studied similar reactions of oxazaphosphorinanes 1.96 (R = Ph, SPh) [356], These reactions are performed in a two-step fashion, and olefin formation requires activation with PhjCOTf in the presence of 2,6-hrtidine. 

A series of 1,3,2-oxazaphosphorinanes (62) has been prepared for conformational studies. Some new seven-membered ring phosphoramidites (63) and diamidites (64) have been synthesised. 

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