An Optically Active Phospholene Oxide

Abstract

the CND0/2 and nb-initio calculationsra1, which show the reliability of the approximation chosen.In the 'H-NMR spectrum of the cation [C,H,]' Olah eta/.r3J found at room temperature one single signal which was split at lower temperatures. These authors -100' Table. Localized three-center molecular orbitals. \ I I Linear combination coefficients Atom i Function i [C,H,]+ ~ B,H, 1 B,H,, ab lriitio [8] [a] C', B' 0.1995 0.0404 H 0.0404 0 0 0.4208 0.3632 ' 0.2143 Localized proportion (%) 96.1 [a] The linear combination coefficients of C N D O calculations refer to orthogonalized (Lowdin) atomic orbitals and thus their absolute values in bonding molecular orbitals aregreater than thecorresponding coefficients in ab-initio calculations which refer to ordinary nonorthogonal atomic orbitals. assigned the structure of a o-complex to the solvated cation. According to our calculations the %-complex should be more stable in the gas phase. This need not contradict our results since 7t-and o-complexes can differ considerably in their solvation energies and in their interaction with the counter-ion. Recently Helgstrand[" reported CND0/2 calculations on the o-complex of [C,H,]'. This author's results agree well with ours, especially as regards bond angles and CH distances.We have been able to prepare the levorotatory form of 3-methyl-l-(p-diethylaminophenyl)-2-phospholene I-oxide ( I ) via its salt with (+)-9-camphorsulfonic acid. To thebest of our knowledge this is the first resolution of a chiralic phosphacyclic compound ['].Methylene chloride solutions of ( I ) [ * , 31 (16.5 mmol in 10ml) and (t )-9-carnphorsuIfonic acid (previously dried in vacuum over P,O, ; 16.2mmol in 160ml) were thoroughly mixed and the solvent subsequently removed in vacuum. The residual syrup was dissolved in 75 ml boiling benzene and the hot solution rendered slightly turbid by addition of 3-4ml n-heptane. By very slow and careful cooling, approximately 4.1 g of the camphorsulfonate of ( I ) could be obtained. After double recrystallization from benzene with a little n-heptane the specific rotation and melting point were constant ([a];'= -40.3' (benzene); m.p. 103-104°C). The difference between the UV spectrum (in cyclohexane) of compound ( I ) (A,,, = 277 nm ; log E = 4.45) and that of the salt (I.,,, = 281 nm ;log E = 3.03) shows that an ammonium (and no phosphonium) salt is present.

Resolution of P-stereogenic P-heterocycles via the formation of diastereomeric molecular and coordination complexes (a review)

“…Ostrogovich and Kerek elaborated the resolution of 1-(4-diethylaminophenyl)-2-phospholene oxide by forming diastereomeric salts with camphorsulfonic acid. 28 Kobayashi et al described the optically active borane complex of 1-phenylphospholane-2carboxylic acid prepared via optical resolution by applying quinine. 29 For the preparation of optically active phosphonium salts, the silver salt of dibenzoyl-tartaric acid, camphorsulfonic acid or menthoxy-acetic acid finds wide-spread application.…”

Preparation of enantiopure 1‐isopentyl‐3‐methyl‐3‐phospholene 1‐oxide via the formation of diastereomeric complexes

“…Resolution methods developed for the separation of the antipodes of racemic P ‐heterocycles may be classified based on the interaction between the substrate and the resolving agent. The resolutions can be achieved via the formation of covalent diastereomers, diastereomeric salts, or diastereomeric complexes . There are also a few examples for the enantiomeric separation of cyclic P ‐stereogenic compounds on a chiral stationary phase …”

Resolution of 1‐n‐Butyl‐3‐Methyl‐3‐Phospholene 1‐Oxide With TADDOL Derivatives and Calcium Salts of O,O'‐Dibenzoyl‐(2R,3R)‐ or O,O'‐di‐p‐Toluoyl‐(2R,3R)‐tartaric Acid

“…The separation of enantiomers of several secondary and tertiary phosphine oxides with a stereogenic center either on the phosphorus atom or on the backbone was accomplished via molecular complex formation with O,O'dibenzoyl-(2R,3R)-tartaric acid. [7][8][9][10][11][12][13][14][15] In some special instances, the bromocamphorsulfonic acid, 3,16,17 camphorsulfonic acid, 17 mandelic acid, 18,19 2,2-dihydroxy-1,1-binaphthalene, 18,20 as well as the α-methylbenzylamine 21 were also used successfully to prepare optically active phosphine oxides.…”