Investigation of the Effects of the Structure and Chelate Size of Bis-oxazoline Ligands in the Asymmetric Copper-Catalyzed Cyclopropanation of Olefins: Design of a New Class of Ligands
作者:Ashutosh V. Bedekar、Elise B. Koroleva、Pher G. Andersson
DOI:10.1021/jo962021a
日期:1997.4.1
D-tartaric acid, two sets of ligands (6b-e and 7a,b) were synthesized and evaluated in the copper-catalyzed cyclopropanation of olefins. The comparison of benzyl and isopropyl derivatives of these ligands with previously reported five- and six-membered bis-oxazolines clearly indicates the beneficiary effect of the larger chelate size and the chiral tether of the tartrate-derived ligand. The effect of the different
Highly isotactic optically active methacrylate polymers by free radical cyclopolymerization
作者:Shiying Zheng、Dotsevi Y. Sogah
DOI:10.1016/s0040-4020(97)00974-5
日期:1997.11
Isospecificfreeradical cyclopolymerization of tartrate-based monomers gives polymers with very high optical rotations. Circular dichroism and polarimetric measurements suggest the polymers are rigid and ordered. Their high resistance to solvolysis suggests potential applications in chiral chromatography.
Evidence for the importance of π-π-attractive interactions in Enantioselective Diels-Alder reactions chiral catalysts of type (RO)2TiCl2
作者:E.J. Corey、Yasushi Matsumura
DOI:10.1016/0040-4039(91)80149-z
日期:1991.10
with Ti(Oi-Pr)4 followed by SiCl4 results in formation of the Ti (IV) complex 5 which is an exceptionally effective catalyst for enantioselective Diels-Alder reactions. The origin of the high enantioselectivities which have been observed (>95 : 5) probably lies in attractive π-π interaction between an aromatic group and the dienophile as indicated in formula 7.
Synthesis of methyl (E)-2-[(3S,4S)-4-hydroxy-3-(pent-3-yloxy)-pyrrolidin-2-ylidene]propanoate and its unusual recyclization
作者:F. A. Gimalova、G. M. Khalikova、V. A. Egorov、A. G. Mustafin、M. S. Miftakhov
DOI:10.1007/s11172-013-0168-0
日期:2013.5
Methyl (2E,4S,5S)-5-hydroxy-6-mesyloxy-2-methyl-4-(pent-3-yloxy)hex-2-enoate was synthesized from l-tartaric acid. Attempted substitution of the mesyloxy group by the reaction with NaN3 directly led to methyl (E)-2-[(3S,4S)-4-hydroxy-3-(pent-3-yloxy)pyrrolidin-2-ylidene]propanoate. The latter on treatment with CF3COOH and then NaOH gave methyl (2E)-2-methyl-4-[(S)-oxiran-2-yl]-4-(pent-3-yloxy)but-2-enoate.
Catalytic Enantioselective One-pot Aminoborylation of Aldehydes: A Strategy for Construction of Nonracemic α-Amino Boronates
作者:Kai Hong、James P. Morken
DOI:10.1021/ja402569j
日期:2013.6.26
We report a strategy for the conversion of aldehydes to enantiomerically enriched alpha-amino boronates through the intermediacy of in situ-generated silylimines. This transformation is brought about by Pt-catalyzed asymmetric addition of B-2(pin)(2) across the imine double bond. An attractive feature of the intermediate diboration adduct is that it can be acylated directly and provides convenient access to important N-acyl alpha-amino boronic ester derivatives.