Enantioselective Synthesis of 4-Substituted 4,5-Dihydro-1H-[1,5]benzodiazepin-2(3H)-ones by the Lewis Base-Catalyzed Hydrosilylation

Abstract

Enantioselective synthesis of 4-substituted 4,5-dihydro-1H-[1,5]benzodiazepin-2(3H)-ones has been accomplished through chiral Lewis base-catalyzed hydrosilylation. The corresponding products were obtained in excellent yields (up to 99%) and enantioselectivities (up to 98%). The absolute configuration of product 3n has been determined as S by X-ray crystallographic analysis.

Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives

“…1); this is the case for example for Malkov and Kocovsky catalyst [4] A or Jones catalyst B [5–6] or the binaphthyldiamine-derived catalyst C developed by our group [7–8]. Also in other systems, such as the Matsumura-type catalysts developed by Zhang [9] of type D , the presence of a proper sterically hindered element seems to be much more decisive than the ability of the tertiary alcohol to make a possible, but not probable, weak hydrogen bond.…”

Trichlorosilane mediated asymmetric reductions of the CN bond

“…The catalysts developed by this group have also been used for the stereoselective synthesis of chiral heterocyclic building blocks such as dihydrobenzoxazinones and dihydroquinoxalinones, 12 and dihydrobenzodiazepinones, 13 using catalysts ent-6 (R 2 = Me) and 8, respectively (Scheme 8). Noteworthy from these reports are the comments on the role of additives; benzoxazinone substrates require water to increase the yield and selectivity, while quinoxalinones and benzodiazepinones do not.…”

An approach to highly efficient reduction of β-enamino esters: A convenient synthesis of β-amino esters

“…[23][24][25][26][27] Recently, a series of organic Lewis base-catalyzed asymmetric hydrosilylations of β-enamino esters for the preparation of chiral β-amino acids were reported. [28][29][30][31][32] In order to attain stereoinduction in the reduction of β-enamino esters and their derivatives, some chiral auxiliaries are also used. 33−37 Among them, a chiral auxiliary [(R)-(+)-phenyl ethyl amine] based diastereoselective β-enamino amide reduction toward sitagliptin was accomplished by treatment with a reducing agent [NaBH 4 / methanesulfonic acid (MsOH)].…”