Stereoselective addition of diphenylphosphine to substituted diphenylethynes: synthetic, NMR and X-ray crystallographic studies

Abstract

The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC᎐ ᎐ ᎐ CRЈ (R = Ph, RЈ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, RЈ = o-tolyl or m-tolyl) yielded Ph 2 PC(R)᎐ ᎐ CHRЈ and/or Ph 2 PCH(R)CH(RЈ)PPh 2 . Proton, 13 C, 13 P and two-dimensional rotating frame Overhauser enhancement 1 H NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield phosphinoalkenes with the Ph 2 P attached to the carbon bearing the least bulky substituent and cis to the olefinic proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give meso/erythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph 2 PH under the same conditions. Crystal structures were determined for E-and Z-Ph 2 P(Ph)C᎐ ᎐ CHPh and show distortions of interbond angles consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and the Mo(CO) 4 complexes of the diphosphinoalkanes were also prepared and their 1 H, 13 C and 31 P NMR spectra recorded. In several cases the pattern of 13 CO NMR signals for the complexes was used unambiguously to determine the stereochemistry of the parent diphosphines.

Catalytic synthesis of vinylphosphanes via calcium-mediated intermolecular hydrophosphanylation of alkynes and butadiynes

“…These vinylphosphanes are well-known substances and a comparison of the NMR parameters verified the formation of 2a [35] and 2b [36,37]. The molecular structures of the (Z)-and (E)-isomers of 2a show distortions of the bond angles as expected for sterically strained alkenes [37].…”

“…The molecular structures of the (Z)-and (E)-isomers of 2a show distortions of the bond angles as expected for sterically strained alkenes [37]. Molecular structure and numbering scheme of 2b is shown in Fig.…”

“…1. Selected structural parameters are compared in Table 1 with literature values [37] of cis-and trans-1,2-diphenyl-1-diphenylphosphanylethene (2a) and of cis-1-phenyl-2-diphenylphosphanylethene (A) [38]. In 2b all PeC bond lengths are very similar and the phosphorus atom is in a pyramidal coordination sphere (angle sum at P1 305.9 ) excluding any p-interaction with the vinyl unit.…”

“…At À15 C 0.51 g of colorless crystals of 2b (1.69 mmol, 85%) precipitated. Physical data were in agreement with literature values [36,37]. 2,4-Hexadiyne (0.22 g, 2.82 mmol) in 18 ml of THF was cooled to À78 C. HPPh 2 (0.98 ml, 1.0 g, 5.63 mmol) and 5 mol-% of [(thf) 4 Ca(PPh 2 ) 2 ] (1) were added.…”

Hydrophosphination of Unactivated Alkenes, Dienes and Alkynes: A Versatile and Valuable Approach for the Synthesis of Phosphines

“…The remaining Eisomer resulted both from the addition of the phosphine to the alkyne and from isomerisation of the Z-isomer. The reaction was then applied to various disymmetric alkynes in order to provide a route to new and unusual diphosphines [63]. However, in all the examples, the E-isomer of the mono-adduct was obtained as the major product together with a small amount of the bis-adduct.…”