New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions
Ten novel hydrogen-bonding catalysts based on open-chain PV-amides of BINOL and chinchona alkaloids as well as three catalysts based on rigid cis-PV-cyclodiphosphazane amides of N1,N1-dimethylcyclohexane-1,2-diamine have been developed. Employed in the asymmetric Michael addition of 2-hydroxynaphthoquinone to β-nitrostyrene, the open-chain 9-epi-aminochinchona-based phosphorus amides show a high catalytic activity with almost quantitative yields of up to 98% and enantiomeric excesses of up to 51%. The cyclodiphosphazane catalysts show the same high activity and give improved enantiomeric excesses of up to 75%, thus representing the first successful application of a cyclodiphosphazane in enantioselective organocatalysis. DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane PV-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by the catalyst.
Klare, Helge,Neudoerfl, Joerg M.,Goldfuss, Bernd
supporting information
p. 224 - 236
(2014/02/14)
ESTERS OF DL-α-TOCOPHEROL AND PHOSPHORIC ACID
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Zhukova, E. E.,Zakharova, E. I.,Sokolova, N. A.,Sarycheva, I. K.,Evstigneeva, R. P.
p. 501 - 504
(2007/10/02)
N,N'-Diphenylphosphorodiamido Chloridate, a Novel Reagent for the Synthesis of Anilides
N,N'-Diphenylphosphorodiamido chloridate (I) is found to be a suitable reagent for the synthesis of anilides (II) of carboxylic acids.A plausible reaction mechanism has been proposed.
Parkhe, Anil B.,Bhai, Aziz,Porwal, K. K.,Boparai, K. S.
p. 79 - 80
(2007/10/02)
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