Toshiaki Morimoto

AN IMPROVED DIPHOSPHINE-IRIDIUM(I) CATALYST SYSTEM FOR THE ASYMMETRIC HYDROGENATION OF CYCLIC IMINES : PHTHALIMIDE AS AN EFFICIENT CO-CATALYST

Abstract The asymmetric hydrogenation of cyclic ketimines, 1-alkyl-3,4-dihydroisoquinolines 5a,b , was carried out with diphosphine-iridium(I) complex catalysts in the presence of various imides or amides as a co-catalyst. Remarkable effects of five-membered imides on the enantioselectivity and the catalytic activity were observed. The enantioselectivity with a BCPM 1 -iridium(I) complex was much improved up to 93% ee by addition of phthalimide.

Efficient asymmetric hydrogenation of α-aminoacetophenone derivatives leading to practical synthesis of (S)-(−)-levamisole☆

The neutral (2S,4S)-MCCPM-rhodium complex was found to be an efficient catalyst for asymmetric hydrogenation of α-aminoacetophenone derivatives. A practical asymmetric synthesis of (S)-(−)-levamisole was realized by using this hydrogenation as a key reaction.

Highly efficient asymmetric hydrogenation of itaconic acid derivatives catalyzed by a modified diop-rhodium complex

Abstract A modified DIOP analogue bearing 4-methoxy and 3,5-dimethyl groups on each phenyl group has been synthesized. The rhodium complex of the ligand has been found to give very high optical yields in the asymmetric hydrogenation of itaconic acid and its derivatives bearing β-aryl groups, the products of which are the key-intermediates for optically active lignan derivatives.

A phosphorus-containing chiral amidine ligand for asymmetric reactions: enantioselective Pd-catalyzed allylic alkylation

Abstract Phosphorus-containing amidine 7 was prepared through several steps from L -valine 1 . The new ligand for asymmetric reactions was evaluated in the palladium-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate and pivalate 8a,b with the nucleophile derived from dimethyl malonate as a preliminary study. Excellent levels of asymmetric induction up to 95% e.e. were achieved along with an efficient conversion.

Preparation of new chiral pyrrolidinebisphosphines as highly effective ligands for catalytic asymmetric synthesis of R-(−)-pantolactone

Abstract New chiral pyrrolidinebisphosphines, MSCPM, PCPM and BCPM, were prepared. Among them, BCPM was found to be the most effective ligand for catalytic asymmetric synthesis of R -(−)-pantolactone.

Enantioselective synthesis of (S)-calycotomine employing catalytic asymmetric hydrogenation with an iridium(I)–(R)-BINAP–phthalimide complex

Abstract An optically active 1-hydroxymethyl-substituted tetrahydroisoquinoline alkaloid, ( S )-calycotomine 1 , was conveniently synthesized by using catalytic asymmetric hydrogenation of 1-benzyloxymethyl-3,4-dihydro-6,7-dimethoxyisoquinoline 6 with 0.5 mol % of an iridium(I) complex of ( R )-BINAP in the presence of 3,4,5,6-tetrafluorophthalimide.

Practical asymmetric synthesis of (R)-(-)-phenylephrine hydrochloride catalyzed by (2R, 4R)-MCCPM-rhodium complex

The neutral chiral N-substituted CPM-rhodium complexes were found to be efficient catalysts for asymmetric hydrogeantion of 3′-benzyloxy-2-(N-benzyl-N-methyl)aminoacetophenone hydrochloride. A practical asymmetric synthesis of (R)-(−)-phenylephrine hydrochloride catalyzed by newly synthesized (2R,4R)-MCCPM-rhodium complex has been achieved.

Enantioselective copper-catalyzed conjugate addition of diethylzinc to enones using new chiral P,N ligands composed of (S)-2-alkyl-2-aminoethylphosphines and α-substituted pyridines

Abstract New P,N ligands prepared from (S)-2-alkyl-2-aminoethylphosphines and α-substituted pyridines are efficient chiral ligands for the copper-catalyzed conjugate addition of diethylzinc to 2-cyclohexen-1-one and chalcone. The best result (90–91% ee) for the cyclohexenone was obtained with Cu(OTf)2 (0.7–1 mol%) and a P,N ligand 4 derived from (S)-1-(diphenylphosphino)-3-methyl-2-butanamine and 6-methylpyridine-2-carboxaldehyde.

Efficient asymmetric syntheses of naturally occurring lignan lactones using catalytic asymmetric hydrogenation as a key reaction

Abstract Optically pure (R)-arylmethylsuccinic acid mono-methyl esters were obtained efficiently by using the catalytic asymmetric hydrogenation of arylidenesuccinic acid monoesters with a rhodium(I) complex of a chiral bisphosphine, (4S,5S)-MOD-DIOP. Asymmetric total syntheses of some naturally occurring lignans, (+)-collinusin, (−)-deoxypodophyllotoxin, and (+)-neoisostegane, were achieved via several steps from (R)-γ-butyrolactones as key intermediates obtained by the reduction of (R)-arylmethylsuccinic acid mono-methyl esters.

Synthesis and application of a novel bisphosphine ligand, (−)-DIOCP, as an unsymmetrized diop to prove the general utility of new designing concept.☆

Abstract A new chiral bisphosphine-Rh complex (DIOCP-Rh) was found to show excellent catalytic activity and good enantioselectivity for the asymmetric hydrogenation of ketopantolactone proving the general utility of new designing concept.