1,3,2-oxazaphosphorinane

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). 

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). 

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. 

In the solid state and in solution, six-membered tetrahedral phosphorus compounds generally adopt a chair as the most stable ground-state conformation. However, Bentrude has shown, by nmr analysis, that the barrier to chairs twist interconversion is low in some six-membered systems (Day et al, 1984 Bentrude et al, 1984 Beres et al., 1987 Nelson et al., 1987). The twist/chair activation barrier for 1,3,2-oxazaphosphorinanes is low. Compound [79] exists in the twist conformation in the solid state and solution. Compound [80] adopts a full boat conformation, from solution nmr spectroscopy and crystal-structure analysis. 

Scheme 3.25 1,3,2-oxazaphosphorinanes from spiro 1,3-amino alcohols. 

Cl5H25N2O2P, cis-2-Oxo-2-dimethylamino-3-phenyl-5-t-butyl-1,3,2-oxazaphosphorinane, 45B, 737 CisHaoNaP, Tris(piperidino)phosphine, 44B, 616 CigHaoNjPSe, Tris(piperidino)phosphine selenide, 45B, 735 ClsHgFgOsP, 2-Phenoxy-2,2-o-phenylenedioxy-4,5-bis(trifluoromethyl)-... 

---