Highly stereoselective and easy synthesis of enantiopure phosphoranyl oxiranes

Chemical Behaviour of a Prototype Boryl(phosphino)carbene

“…In the 13 C{ 1 H} NMR spectrum, the carbon bound to the phosphorus atom resonates at d = 143.8 ppm, with a coupling constant value ( 1 J CP = 61.2 Hz) indicative of direct connectivity between these two atoms, as reported for phosphaalkenes. [12] The absence of any reactivity with Lewis basic reagents, like tert-butylisocyanide [13] or PMe 3 , [8,14] indicates poor electrophilic behaviour of boryl(phosphino)carbene 1.…”

“…The reactions between the phosphino(silyl)carbene and aldehydes have been investigated, and two competitive processes were observed. With aromatic aldehydes, the reaction proceeds through a concerted [2+1] cycloaddition reaction to form a carbonyl group, leading to formation of oxiranes, [13] whereas with alkyl aldehydes a competitive pathway was observed through a [2+2]-like cycloaddition, providing a transient oxaphosphetene that rapidly transforms into the corresponding phosphorylated olefin. [17] The boryl(phosphino)carbene 1 reacts with benzaldehyde to produce exclusively the Z isomer of boryl(phosphoxide)alkene 4 (Scheme 3).…”

“…In the 1 H NMR spectrum, two sets of signals are observed for the diastereotopic hydrogen atoms of the methylene bridge: doublets of doublets at d = 3.11 ( 2 J HH = 5.2, 3 J HP = 27.6 Hz) and 2.99 ppm ( 2 J HH = 5.2, 3 J HP = 53.7 Hz). The solid-state structure of the major diastereomer of 6 was determined by a single-crystal (2), C1ÀCC33 1.522(2), C1ÀC32 1.536(2), P1ÀN1 1.691(1), P1ÀC2 1.862(2), P1ÀC1 1.892(2), B1ÀN2 1.402(2), B1ÀC17 1.593(2), B1ÀC1 1.638(2); C32-C1-P1 117.45(11), C33-C1-C32 58.36(11), C32-C1-B1 117.05 (13), N1-P1-C2 101.66 (7), N1-P1-C1 111.52 (7), C2-P1-C1 107.39 (7), N2-B1-C17 121.27 (14), N2-B1-C1 122.54 (14), C17-B1-C1 116.09 (13).…”

“…Dry and oxygen-free solvents were used. 1 H, 11 B, 13 C and 31 P NMR spectra were recorded on Brucker Avance 400 or Avance 300 spectrometers. 1 H and 13 C NMR chemical shifts are reported in parts per million (ppm) relative to Me 4 Si as an external standard.…”

“…HRMS (ESI + ): m/z calcd for C 34 H 52 BClN 3 P: 580.3759 [M + H] + ; found: 580.3763; the counter-anion was found to be chlorine by HRMS. 4 J PH = 6.0 Hz, 1 H; CH Ar P); 13 Alternative procedure for synthesis of 6: Methylene phosphonium 7 (645 mg, 0.92 mmol) was dissolved in THF (6 mL). The solution was cooled to À80 8C and a solution of potassium hexamethyldisilazide (KHMDS, 275 mg, 1.38 mmol) in THF (2 mL) was added dropwise (185 mg, 0.92 mmol).…”