Highly Enantioselective Synthesis of Pseudo-C₂-Symmetric Axially Chiral Biaryl Diphosphines via Rhodium-Catalyzed Double [2 + 2 + 2] Cycloaddition

Abstract

S11-12Table S1. Crystallographic data for compounds 3a and 4 General Comments. All manipulations involving air-sensitive materials were carried out using standard Schlenk line techniques under an atmosphere of nitrogen or argon in oven-dried glassware.Dichloromethane, 1,2-dichloroethane and chlorobenzene were distilled from calcium hydride. 1,7-octadiyne, ethyl trifluoropyruvate, allylbenzene, silver hexafluoroantimonate, rac-and (R)-BINAP were purchased from commercial suppliers and used without further purification. [RhCl(COD)] 2 , 1 [(cycloocta-1,5-diene)PtCl 2 ], 2 2,8-decadiyne, 3 2,2-di(prop-2-ynyl)malonic acid dimethyl ester 4 2,2-di(but-2-ynyl)malonic acid dimethyl ester 5 and 1,4-bis(diphenylphosphino)buta-1,3-diyne 6 were prepared as previously described. 1 H and 13 C{ 1 H} NMR spectra were recorded on a JEOL LAMBDA 500 or a Bruker AMX 300 instrument. Optical rotations were measured on a Optical Activity PolAAr 2001 digital polarimeter with a sodium lamp and are reported as follows: [ ] D 20 (c g/100 mL, solvent). Thin-layer chromatography (TLC) was carried out on aluminum sheets pre-coated with silica gel 60F 254 and column chromatography was performed using Merck Kieselgel 60. Gas chromatography was performed on a Shimadzu 2010 series gas chromatograph equipped with a split-mode capillary injection system and flame ionization detection using a Supelco Beta DEX column.Analytical high performance liquid chromatography (HPLC) was performed on an Agilent 110 Series HPLC equipped with a variable wavelength detector using a Daicel Chiralcel OD-H or AD-H column. Enantiomeric excesses were calculated from the HPLC and GC profiles. Synthesis of Cycloadduct 3a.A flame-dried Schlenk flask was charged with [RhCl(COD)] 2 (0.027 mg, 0.05 mmol), AgSbF 6 (0.038 g, 0.11 mmol), rac-BINAP (0.069 g, 0.11 mmol) and 1,2-dichloroethane (20 mL).1,4-Bis(diphenylphosphinoyl)buta-1,3-diyne (0.500 g, 1.11 mmol) and 2,2-di(but-2-ynyl)malonic acid dimethyl ester (0.315 g, 1.33 mmol) were added and the resulting solution stirred at 80 °C for 3-4 hr. After this time, the solvent was removed in vacuo to leave a crude brown solid which was purified by column chromatography eluting with ethyl acetate/acetone (4:1) to yield the product as a beige solid (0.702 g, 92%).

Phosphines and related C–P bonded compounds

“…Sulfonation of the hydrophobic phosphine n-C 12 H 25 OC 6 H 4 P(anisyl-p) 2 has given a new amphiphilic phosphine useful as a ligand that also promotes micelle-formation in the aqueous biphasic catalytic hydroformylation of long chain alkenes. 153 A series of heteroaryl-substituted benzylic P, N ligands (109) has been prepared from diphenyl(o-tolyl)phosphine via a sequence of metallation and carboxylation reactions at the methyl group, followed by construction of the heterocyclic ring substituent. The same paper also reports a different route to related ligands having geminaldimethyl substitution at the benzylic carbon, which finishes with a conventional aryl lithium-chlorophosphine step.…”

“…103 Trichlorosilane-amine combinations have also been used in the final stage of the synthesis of various ether-bridged chiral diphosphinobiaryl ligands, e.g., (74), 104 (75), 105 and (76), 106 and of the chiral Norphos system (77). 107 A combination of trichlorosilane with triethylphosphite was the chosen reagent for reduction of the dioxides of the chiral atropisomeric diphosphines (78) 108 and (79), 109 both systems being accessed via cycloaddition reactions of alkynylbisphosphine oxides. Other silane reagents…”

The Synthesis of Chiral Phosphorus Ligands for use in Homogeneous Metal Catalysis

“…[24] Doherty et al claimed the synthesis of some new atropisomeric diphosphines based on the [2+2+2] cycloaddition of 1,4-diarylphosphino-butadiyne with tethered diynes (Scheme 3). [25] The biaryl backbone was stepwise constructed. In the opening step a racemic Rh-catalyst was used for the first [2+2+2] cycloaddition.…”

Recent development for enantioselective synthesis of aromatic compounds from alkynes via metallacyclopentadienes

“…The reaction of 1,6‐diyne 43 with phosphonate‐substituted 1,3‐butadiyne 44 in the presence of the similar catalyst gave the corresponding chiral biaryl diphosphonate 45 in high yield with outstanding ee (entry 2) [10]. The similar biaryl diphosphonate 47 was also synthesized using a Rh(I)BINAP catalyst in good yield and with high enantioselectivity (entry 3) [11].…”