Experimental and Computational Study of Steric and Electronic Effects on the Coordination of Bulky, Water-Soluble Alkylphosphines to Palladium under Reducing Conditions: Correlation to Catalytic Activity
摘要:
Sterically demanding, water-soluble alkylphosphine ligands 2-(di-tert-butylphosphino)ethyltrimethylammonium chloride (t-Bu-Amphos) and 4-(di-tert-butylphosphino)-N,N-di-methylpiperidinium chloride (t-Bu-Pip-phos) in combination with palladium salts provided active catalysts for the cross-coupling of aryl halides under mild conditions in aqueous solvents, whereas 4-(dicyclohexylphosphino)-N,N-dimethylpiperidinium chloride (Cy-Pip-phos) gave a less active catalyst. Catalyst activity increased with increasing cone angle of the ligands, but the chi electronic parameter determined from the symmetric C-O stretching frequency of LNi(CO)(3) did not correlate with catalyst activity. Catalyst activity correlated with other calculated electronic parameters, such as the HOMO-LUMO energy gap of the ligand and the HOMO energy level of the LPd(0) species. Multinuclear NMR spectroscopic studies showed that t-Bu-Amphos and t-Bu-Pip-phos rapidly form L2Pd(0) (L = t-Bu-Amphos or t-Bu-Pip-phos) complexes when reacted with Pd(OAc)(2) under reducing conditions over a range of L:Pd ratios. In contrast, the coordination chemistry of Cy-Pip-phos depended on the Cy-Pip-phos:Pd ratio. At a less than or equal to 1: 1 Cy-Pip-phos:Pd ratio, rapid formation of L2Pd(0) occurred. At higher L:Pd ratios, initial formation of trans-(Cy-Pip-phos)(2)PdCl2 was observed followed by slow reduction to the Pd(0) complex.
Sterically Demanding, Water-Soluble Alkylphosphines as Ligands for High Activity Suzuki Coupling of Aryl Bromides in Aqueous Solvents
摘要:
[GRAPHICS]Sterically demanding, water-soluble alkylphosphines have been found to give highly active catalysts for Suzuki coupling of aryl bromides in aqueous solvents. A variety of aryl bromides and boronic acids were coupled in excellent yield. Turnover numbers up to 734 000 mmol/mmol Pd have been achieved under mild conditions.
HOMOGENEOUS ERYTHROPOIETIN AND METHOD FOR THEIR PREPARATION
申请人:Sloan-Kettering Institute for Cancer Research
公开号:EP2010556B1
公开(公告)日:2015-09-23
Homogeneous Erythropoietin and Other Peptides and Proteins, Methods and Intermediates for Their Preparation
申请人:Danishefsky Samuel J.
公开号:US20100081786A1
公开(公告)日:2010-04-01
The present invention provides isolated homogeneous polyfunctionalized proteins (e.g., erythropoietin), isolated glycopeptides, and a method for preparing polyfunctionalized peptides and/or proteins via cysteine-free native chemical ligation. In certain embodiments, the invention provides an isolated homogeneous polyfunctionalized protein having the structure (I). In certain other embodiments, the invention provides an isolated glycopeptide having Formula (II). In certain other embodiments, the inventive method is a method for preparing a polyfunctionalized peptide comprising a peptidic backbone made up of four or more amino acids, wherein two or more non-adjacent amino acids are independently substituted with a moiety having the structure (III)-LH. wherein A and L1 are as defined herein.
US8754192B2
申请人:——
公开号:US8754192B2
公开(公告)日:2014-06-17
Sterically Demanding, Water-Soluble Alkylphosphines as Ligands for High Activity Suzuki Coupling of Aryl Bromides in Aqueous Solvents
作者:Kevin H. Shaughnessy、Rebecca S. Booth
DOI:10.1021/ol0163629
日期:2001.8.1
[GRAPHICS]Sterically demanding, water-soluble alkylphosphines have been found to give highly active catalysts for Suzuki coupling of aryl bromides in aqueous solvents. A variety of aryl bromides and boronic acids were coupled in excellent yield. Turnover numbers up to 734 000 mmol/mmol Pd have been achieved under mild conditions.
Experimental and Computational Study of Steric and Electronic Effects on the Coordination of Bulky, Water-Soluble Alkylphosphines to Palladium under Reducing Conditions: Correlation to Catalytic Activity
作者:Rebecca B. DeVasher、Jason M. Spruell、David A. Dixon、Grant A. Broker、Scott T. Griffin、Robin D. Rogers、Kevin H. Shaughnessy
DOI:10.1021/om049241w
日期:2005.2.1
Sterically demanding, water-soluble alkylphosphine ligands 2-(di-tert-butylphosphino)ethyltrimethylammonium chloride (t-Bu-Amphos) and 4-(di-tert-butylphosphino)-N,N-di-methylpiperidinium chloride (t-Bu-Pip-phos) in combination with palladium salts provided active catalysts for the cross-coupling of aryl halides under mild conditions in aqueous solvents, whereas 4-(dicyclohexylphosphino)-N,N-dimethylpiperidinium chloride (Cy-Pip-phos) gave a less active catalyst. Catalyst activity increased with increasing cone angle of the ligands, but the chi electronic parameter determined from the symmetric C-O stretching frequency of LNi(CO)(3) did not correlate with catalyst activity. Catalyst activity correlated with other calculated electronic parameters, such as the HOMO-LUMO energy gap of the ligand and the HOMO energy level of the LPd(0) species. Multinuclear NMR spectroscopic studies showed that t-Bu-Amphos and t-Bu-Pip-phos rapidly form L2Pd(0) (L = t-Bu-Amphos or t-Bu-Pip-phos) complexes when reacted with Pd(OAc)(2) under reducing conditions over a range of L:Pd ratios. In contrast, the coordination chemistry of Cy-Pip-phos depended on the Cy-Pip-phos:Pd ratio. At a less than or equal to 1: 1 Cy-Pip-phos:Pd ratio, rapid formation of L2Pd(0) occurred. At higher L:Pd ratios, initial formation of trans-(Cy-Pip-phos)(2)PdCl2 was observed followed by slow reduction to the Pd(0) complex.