Jerzy Szewczyk

The formation of P(III) products from phosphinamides with silicon hydrides

Abstract Two N,N-diethyl derivatives of phosphinamides in the 3-phospholene series were used as models to develop techniques for reduction to P(III) derivatives. The products from the reduction with HSiCl3 in the presence of pyridine depended on the molar ratio of the participants. A 1 : 1 : 1 amide-HSiCl3-pyridine mixture after 2 h in refluxing benzene provided the phosphinous chlorides in preparatively useful (55–65%) yield. A 1 : 1.5 : 1.5 mixture led to coupling at phosphorus to give the diphosphine, also in good yield (60–65%). The diphosphines also resulted from refluxing a 1 : 1 mixture of the amide with phenylsilane. However, heating a 2 : 1 amide–silane mixture at 100° gave only the product of deoxygenation (65%). A 1-benzylaminophosphetane oxide was also reduced successfully. The conditions with HSiCl3 and C6H5SiH3 were applied to a noncyclic phosphinamide (C6H5)2PO(NEt2); reaction rates were considerably slower than for the cyclic amides, but similar P(III) products were formed. 13C and 31P NMR...

Thionin oxide as a Possible Intermediate on Periodate Oxidation of 9-Thiabicyclo[6.1.0]nona-2,4,6-triene

Abstract 9-Thiabicyclo[6.1.0]nona-2,4,6-triene was oxidized at −15 to −20°C with sodium periodate in a methanol-water medium. The major isolated product was established as cis 3a,7a-dihydrobenzo[b]thiophene- cis -1-oxide, which is best explained as arising from intramolecular cycloaddition of a thionin oxide intermediate.

COMPARATIVE STUDIES ON SYNTHESIS AND PROPERTIES OF PHOSPHORUS AND SULFUR HETEROCYCLES: THE HETERONIN OXIDE SYSTEM

Abstract Phosphonin oxides are the first recognizable product on reaction of 9-phosphabicyclo[6.1.0]nona-2,4,6-trienes with peroxides at −15°C. These compounds (R = C6H5 or t-C4H9) are stable below −15°C, but undergo intramolecular cycloaddition to give trans-3a,7a-dihydrophosphindoles on warming to room temperature. The reaction applied to the sulfur counterpart of the phosphine gave only the 9-thiabicyclo[4.2.1]nonatriene system, but oxidation with sodium periodate at −15°C gave a 34% yield of a product identified conclusively as cis-3a,7a-dihydrobenzo[b]thiophene oxide, which must have arisen from a thionin oxide. This is the first evidence for the formation of a noncyclic thionin derivative.

A LINEAR CORRELATION BETWEEN THE P-31 NMR SHIFTS OF CYCLIC PHOSPHINES AND THE 0–17 SHIFTS OF THE CORRESPONDING PHOSPHINE OXIDES

Abstract The O-17 NMR shifts for phosphine oxides based on six different heterocyclic ring systems, representing 16 data points, were plotted against the P-31 shifts of the corresponding phosphines. A linear correlation with R = 0.96 resulted. Each heterocyclic system occupied its own region of the correlation line, with no overlap. There was no correlation between the O-17 NMR shifts and the P-31 shifts of the phosphine oxides.

Synthesis of 1,2-oxaphospholane oxides by oxygen insertion into the C-P bond of phosphetane oxides

Abstract A number of phosphetane oxides with a variety of aromatic substituents on phosphorus underwent oxygen insertion into a C—P bond by the action of m-chloroperbenzoic acid, resulting in formation of 1,2-oxaphospholane oxides in high yield. The products were easily isolated and were characterized by 31P and 13C NMR. For 2,2,3,4,4-pentamethyl-substituted phosphetane oxides only one site of attack is possible and the reaction is assumed to proceed with retention of the stereochemistry of the starting material. For 2,2,3-trimethyl-substituted phosphetane oxides, regioisomers were formed, with that derived from O-insertion at the least substituted carbon accounting for 80–90% of the product.

Fragmentation Reactions of Bridged Heterocyclic Phosphorus Compounds as a Source of Low-Coordination Species

Abstract Several types of unsaturated, bridged structures have been prepared that can undergo retro-cycloaddition with the extrusion of phosphorus species having low coordination. By this technique, the species RO-PO2, R-PO2, R2N-P=S, RO-P=S, and R-P=CH2 have been generated and detected by trapping experiments.

Unusual properties of chloro- and amino-phosphines in the 7-phosphanorbornene series

Phosphinamides based on the 7-phosphanorbornene framework can be reduced with HSiCl3–C5H5N to give phosphinous chlorides which have remarkable chemical and 31P n.m.r.properties and a strong preference for an anti-configuration of chlorine.

The synthesis, X-ray crystal structure, and solution characterization of a bis(diphosphine)-bridged dirhodium(I) complex containing a Rh2P4 six-membered ring

The preparation of [{Rh(cod)}2(µ-L1)2][BF4]2(1) from ([graphics omitted])2(L1) and [Rh(cod)2]-BF4(cod = cyclo-octa-1,5-diene) is described. The compound crystallizes in the monoclinic space group P21/c(C52h), with a= 9.650(1), b= 11.609(1), c= 21.884(3)A, β= 117.07(1)°, and Z= 2. The structure was refined to R= 0.033 for 3 434 reflections. The solid-state structure shows two diphosphine ligands L1 bridging two rhodium(I) atoms to form a six-membered Rh2P4 ring in a chair conformation. Solution studies (1H and 13C-{1H} variable-temperature n.m.r. spectra) exhibit characteristics of a ring inversion equilibrium with ΔG271= 14.0(0.2) kcal mol–1. Computer simulation of the 31P-{1H} n.m.r. spectrum is used to analyse the internuclear couplings of the AA′A″A‴XX′ pattern (A =31P, X =103Rh). The bridging diphosphine ligands exhibit a deshielding effect on the trans olefinic carbon atoms of cod in (1) which is in the range normally found for phosphine ligands.

7-Phosphanorbornene derivatives as precursors of esters and amides of two-co-ordinate thiophosphenous O-acid

Heating thiophosphinate O-esters and thiophosphinamides having the 7-phosphanorbornene framework results in elimination of fragments that are derivatives of thiophosphenous O-acid; they are trapped by cycloaddition with 2,3-dimethylbutadiene to form 2,5-dihydrophospholes.