Stereoselective reduction of (S)-4-isopropyl-3-phenacyl-1,3-oxazolidin-2-one by means of 1,4-asymmetric induction: Synthesis of chiral 2-amino-1-phenylethanols.
The reactions of (S)-4-amino-1-phenylbutanones (3a-e) with methyllithium, methylmagnesium bromide, and methyltitanium triisopropoxide were studied. The reaction of the (S)-4-hydroxyethylamino derivatives (3a and 3d) with methyltitanium triisopropoxide gave 4a and 4d by 1, 6-asymmetric induction with diastereoselectivities of 78 and 70%.
Stereoselective reduction of (S)-4-isopropyl-3-phenacyl-1,3-oxazolidin-2-one by means of 1,4-asymmetric induction: Synthesis of chiral 2-amino-1-phenylethanols.
Stereoselective reductions of (S)-4-isopropyl-3-phenacyl-1, 3-oxazolidin-2-one (2) with several complex metal hydrides gave 2-4'-isopropyl-2'-oxo-1', 3'-oxazolidinyl-1-phenylethanol (3) and 2-N-1'-isopropyl-2'-hydroxyethyl-N-methylamino-1-phenylethanol (4) in good yields. These products were diastereomeric mixtures and the diastereomer ratios were estimated to be ca. 75 : 25. The asymmetric 2-amino-1-phenylethanols (major products of 3 and 4) were easily isolated by recrystallization. The absolute configuration of (1S, 4'S)-3 was determined by X-ray analysis. The reductions of (S)-4-isopropyl-1-phenacyl-1, 3-oxazolidine (6) with complex metal hydrides gave 2-4'-isopropyl-1', 3'-oxazolidinyl-1-phenylethanol (7) and 4 as diastereomeric mixtures (ca. 70 : 30).
The title rearrangement of the chiral (E-crotyloxy)acetamides derived from (S)-prolinol has been shown to provide a modest level of asymmetricinduction (52–60%) along with a high erythro-selectivity (95–98%). The influence of the metal centers (Li, K, and Zr) and the ligating substituents on the prolinol part has been discussed.
[EN] CHIRAL CATALYSTS FOR ENANTIOSELECTIVE SYNTHESIS
申请人:RESEARCH CORPORATION TECHNOLOGIES, INC.
公开号:WO1991014672A1
公开(公告)日:1991-10-03
(EN) A chiral catalyst is disclosed together with methods of using it for enantioselective syntheses. The chiral catalyst includes a nucleus with two metal atoms that has four bridging ligands oriented radially to the axis of the nucleus. Each of these ligands includes a two complexing atoms each complexed to one of the metal atoms. At least one of the bridging ligands includes a chiral center which is bonded to one of the complexing atoms. Preferably, all four of the bridging ligands include a chiral center bonded to one of the complexing atoms. The catalyst of the invention has been found to be useful in catalyzing carbenoid transformation reactions such as cyclopropanation.(FR) Catalyseur chiral et procédés d'utilisation de ce catalyseur pour des synthèses énantiosélectives. Le catalyseur chiral comporte un noyau avec deux atomes de métal qui a quatre ligands de pontage orientés radialement à l'axe du noyau. Chacun de ces ligands comporte deux atomes complexants, chacun étant complexé à un des atomes de métal. Au moins un des ligands de pontage a un centre chiral qui est lié à un des atomes complexants. De préférence, l'ensemble des quatre ligands de pontage comportent un centre chiral lié à un des atomes complexants. Le catalyseur de la présente invention s'est avéré utile pour catalyser des réactions de transformation carbénoïde, telle que la cyclopropanation.