Zinc-Mediated Hydroxyallylation of Aldehydes with Cyclopropanols: Direct Access to Vicinal <i>anti</i>-<i>sec</i>,<i>tert</i>-Diols via Enolized Homoenolates
作者:Yoshiya Sekiguchi、Naohiko Yoshikai
DOI:10.1021/acs.orglett.1c04331
日期:2022.1.28
by zinc-mediated α-hydroxyallylation of aldehydes with cyclopropanols. The reaction features the action of the zinc-enolized homoenolate as a γ-oxyallyl nucleophile toward the carbonyl electrophile. The diastereoselectivity of the present reaction is ascribed to the strong preference for a chelated (Z)-configuration of the enolized homoenolate as well as the bicyclic chairlike transition state it forms
[EN] 3-SUBSTITUTED PARA-MENTHANE DERIVATIVES<br/>[FR] DÉRIVÉS DE PARA-MENTHANE 3-SUBSTITUÉS
申请人:GIVAUDAN SA
公开号:WO2014009416A1
公开(公告)日:2014-01-16
A compound of formula (I), wherein the symbol, formula (II), represents a double bond when X is an oxygen atom or a single bond when X is a hydroxyl group, and Y represents a hydrogen atom or a substituent in the meta or para position, the substituent if present being hydroxyl, CN or -CH2CN, useful as a cooling compound.
Enantioselective catalysis. Part 119: New chiral 2-(2-pyridinyl)oxazoline ligands containing an additional optically active substituent in the pyridine system
作者:Henri Brunner、Reinhard Störiko、Bernhard Nuber
DOI:10.1016/s0957-4166(97)00619-8
日期:1998.2
The synthesis of novel chiral nitrogenligands and their precursors is described. They consist of an opticallyactive oxazoline bound to pyridine in the 2-position. In addition, another opticallyactive substituent is attached to the pyridine ring. The effect of the two independent stereogenic units in one ligand was studied in the Rh(I)-catalysed enantioselective hydrosilylation of acetophenone with
A synthetic approach to the cis-fused marine pyranopyrans, (3E)- and (3Z)-dactomelyne. X-ray structure of a rare organomercurial
作者:Alan P. Kozikowski、Jaemoon Lee
DOI:10.1021/jo00290a014
日期:1990.2
Synthesis and characterization of chiral (-)-menthyltin(IV) compounds. X-ray structure of tert-butyl-8-(dimethylamino)naphthyl-(-)-menthyltin hydride
作者:Herbert Schumann、Birgit C. Wassermann、F. Ekkehardt Hahn
DOI:10.1021/om00044a019
日期:1992.8
A series of optically active (-)-menthyltin(IV) derivatives with tin directly bound to a chiral carbon atom has been synthesized and characterized. The Grignard reagent derived from (-)-menthyl chloride stereospecifically reacts with trimethyltin chloride to afford (-)-menthyltrimethyltin (1). 1 is derivatized by selective bromodemetalation, alkylation, and hydrogenation, yielding (-)-menthyldimethyltin bromide (2), tert-butyl-(-)-menthyldimethyltin (3), tert-butyl-(-)-menthyltin dibromide (4), and each prochiral at the tin center as well as tert-butyl-8-(dimethylamino)naphthyl-(-)-menthyltin bromide (5) and hydride (6), in which an additional center of asymmetry has been created at the tin atom. By means of multinuclear NMR investigations, the conformation of the optically active ligand in 1-6 was determined, the coordination behavior of the potentially bidentate aminonaphthyl ligand in 5 and 6, resulting in a trigonal bipyramidal (5) or a distorted tetrahedral (6) structure in solution, was established, and for 5 and 6, the ratio of epimers differing in the absolute configuration at the tin center was determined to be 45:55 and 40:60, respectively. The single-crystal X-ray structural analysis of 6 revealed a pair of R(Sn)/S(Sn) epimers. 6 crystallizes monoclinically, space group P2(1), with a = 17.786 (8) angstrom, b = 10.890 (4) angstrom, c = 13.700 (8) angstrom, beta = 108.0 (4)-degrees, and Z = 4. The structure was solved from 4449 observed reflections with I greater-than-or-equal-to 3-sigma(I) and refined to a final R factor of 0.028. The coordination geometry around tin for the two molecules in the asymmetric unit is that of a trigonal bipyramidal-like monocapped tetrahedron showing a very weak Sn-N interaction with a Sn-N distance of 2.931 (3) (molecule A) or 2.885 (3) angstrom (molecule B). The Sn-H bond lengths are 1.52 (5) and 1.63 (5) angstrom, respectively.