Dual Stereochemical Control in Reaction of Di- and Trialkyl Phosphites with Aldimines

Stereochemistry of addition of di- and trialkyl phosphites to C=N compounds was investigated. Reactions of achiral dialkyl phosphites with chiral aldimines as well as that of chiral di-(1R,2S,5R)-menthyl phosphite with achiral aldimines result in low diastereomeric enrichment of the addition compound. Reaction stereoselectivity increased when supplementary chiral inductor was introduced to the reaction system. Reaction of di-(1R,2S, 5R)-menthyl phosphite with (S)-α-methylbenzylbenzaldimine proceeds as concerted asymmetric induction to form practically one diastereomer of N-substituted aminophosphonic acid. However, reaction of di-(1R,2S, 5R)-menthyl phosphite with (R)-α-methylbenzylbenzaldimine proceeded as not concerted asymmetric induction, and diastereomeric enrichment of the product was low. By chemical extrapolation, absolute configuration of compounds formed was established. Tri-(1R,2S,5R)-menthyl phosphite reacts with C=N compounds in the presence of boron trifluoride etherate to form aminophosphonic acid derivatives with the absolute configuration opposite to that appearing in the reaction of di-(1R,2S,5R)-menthyl phosphite with the same C=N compounds.     

Recombination of nonequilibrium current carriers in n-InAs1−x−ySbxPy

The stationary photoconductivity, the photomagnetic effect, and the relaxation kinetics of photoconductivity in n-InAs_1–x–ySb_xP_y crystals (x=0.06, y=0.11) with n₀ = 8·10¹⁵ and 3·10¹⁶ cm^–3 were measured and the lifetimes of nonequilibrium current carriers in the temperature interval T=78–295 K were determined. The possible mechanisms of recombination, which limit the lifetimes (radiative _R, Auger recombination _A, and recombination through centers with E_f=0.13 eV), which, as is demonstrated, are determined by interband recombination processes with _RA = _RA/(_R + _A), are calculated theoretically. The contribution of the 0.13 eV recombination centers can be significant when n₀10¹⁴ cm^–3.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 52–54, April, 1991.     

STEREOSELECTIVE REACTIONS OF CHIRAL AMINES WITH RACEMIC CHLOROPHOSPHINES

Racemic chlorophosphines react stereoselectively with chiral l-phenylethylamines or amino acid esters to give diastereomerically enriched aminophosphines 3, which were isolated as diastereomerically pure crystalline borane complexes. Oxidation, thionation, the reaction with methyl iodide provide optically active derivatives of aminophosphines. (R,S)- and (S,S)-stereomers of phosphinic acid amides were separated by crystallization and a flash-chromatography. The stereochemical properties of phosphorus acid amides were investigated. The mechanism of asymmetric induction at the trivalent phosphorus atom was rationalized.     

Some Unusual Reactions in Organophosphorus Chemistry

Methylenephosphinophosphorane 1 reacts with azides without evolution of nitrogen to give zwitterionic phosphorazide 3 and iminophosphorazide 4 , which are in equilibrium to each other; 1 reacts with hexafluoroacetone (HFA) in a different way to give zwitterionic product 5 , which may have the ylidic structure 5' . HFA and thio-HFA react analogously with methylenediphosphines 6 to give corbodiphosphoranes 7 . Reaction of 6 with activated alkenes 9 gives monoylide 10 , which is a useful synthone for the synthesis of fluorosubstituted conjugated triene 12 and diylides 13 and 14 . Reaction of 10 with TOB gives unusually stable betaine 15 . Reaction of the other activated alkene 16 with 6 unexpectedly gave the unusual zwitterionic compound 17 .     

Stereoselective Reactions of Optically Active Derivatives of α-Methylbenzylaminophosphine

A number of N-(-methylbenzyl) phosphorus amides were synthesized, and their stereochemical properties were studied. Reactions of achiral chlorophosphines with optically active -methylbenzylamine are accompanied by asymmetric induction at the phosphorus atom to give optically active diastereoisomers of N-(-methylbenzyl)aminophosphines, which were isolated as the corresponding borane complexes with 100% optical purity. Stereochemically pure (R,S)-aminophosphines were obtained by decomposition of these complexes via treatment with diethylamine. Their oxidation, sulfurization, and alkylation with methyl iodide afforded optically active aminophosphine derivatives. Hydrolysis of (R,S)-aminophosphines gave optically active tert-butylphenylphosphine oxide and phosphonic acid amides. (R,S)- and (S,S)-Diastereoisomers of N-(-methylbenzyl)phosphinic amides were separated by crystallization and flash chromatography, and their absolute configuration was established. Also, derivatives of bis- and tris(-methylbenzylamino)phosphines were synthesized.     

Synthesis and Reactivity of α-Bromo-4-(difluoromethylthio)acetophenone

A synthesis is reported for -bromo-4-difluoromethylthioacetophenone and the conditions for the condensation of this compound with 2-aminothiazole, 2-amino-5-chloropyridine, 2-amino-4,5-dihydro-3H-pyrrole, benzimidazoline-2-thione, oxadiazoline-2-thione, and thiourea were studied. S- and N-substituted azaheterocycles containing the 4-(difluoromethylthio)phenyl fragment were synthesized and characterized.     

Synthesis of Pyrrolo[2,1-<Emphasis Type="Italic">b</Emphasis>]thiazol-3-one Derivatives

Summary. Ethyl [4-oxo-3-(2-oxo-2-arylethyl)thiazolidin-2-ylidene]acetates and [4-oxo-3-(2-oxo-2-arylethyl)thiazolidin-2-ylidene]acetonitriles were shown to react with substituted benzaldehydes at the endocyclic methylene group leading to the corresponding 5-arylmethylidene derivatives. Their treatment with DMF · POCl₃ complex yielded 3-oxo-5-aroyl-2-arylmethylidene-2,3-dihydropyrrolo[2,1-b]thiazole-7-carboxylic acids ethyl esters and -7-carbonitriles. The structures of the pyrrolothiazoles were confirmed by an X-ray crystallographic study, which indicated the (Z)-configuration at the arylmethylidene moiety.     

A novel type of formation of zwitterionic compounds,containing two phosphorus atoms of opposite charge and different coordination number

The oxidation of bis[bis(dialkylamino)phosphinyl]methane 1 with 5,5,5-trifluoro-4-(trifluoromethyl)penta-3-en-2-one 2 unexpectedly gave zwitterionic compound 7 which according to X-ray analysis contains two phosphorus atoms of opposite charge and different coordination number (lambda 4P(+); lambda 6P(-)) with a direct P-H bond at the hexacordinated phosphorus.