New S,O-acetals from (1R)-(−)-myrtenal as chiral auxiliaries in nucleophilic additions
摘要:
Treatment of hydroxythiol 4 with alpha,alpha-diethoxyacetophenone at room temperature yielded a mixture of epimeric S,O-acetals 6 and 7 (1:4. 92%, yield), which were efficiently separated by flash chromatography. The OTBS derivatives 8 and 9 were treated with several Grignard reagents to afford carbinols 10 and 13 respectively (85-99%, yield, >95% dr). After successive hydrolysis and reduction of 10 and 13 it is possible to obtain either enantiomer of diols 16 in high optical purity (>95% er). (C) 2004 Elsevier Ltd. All rights reserved.
Electronic polarizability-based stereochemical model for Sharpless AD reactions
作者:Peng Han、Ruji Wang、David Zhigang Wang
DOI:10.1016/j.tet.2011.09.073
日期:2011.11
controlling absolute stereochemical courses of general asymmetric induction events. Thus, a sensitive dependence of the sense of chiral induction on an alkene substrate’s substituent electronic polarizability character was uncovered from a range of structurally highly comparable Sharpless asymmetric dihydroxylation (AD) systems, from which a new polarizability-based stereochemicalmodel of predictive power
Enecarbamates as Selective Substrates in Oxidations: Chiral-Auxiliary-Controlled Mode Selectivity and Diastereoselectivity in the [2+2] Cycloaddition and Ene Reaction of Singlet Oxygen and in the Epoxidation by DMD and <i>m</i>CPBA
作者:Waldemar Adam、Sara G. Bosio、Nicholas J. Turro、Barbara T. Wolff
DOI:10.1021/jo035745c
日期:2004.3.1
The stereochemical course of the oxidation of chiral oxazolidinone-substituted enecarbamates has been studied for singletoxygen (1O2), dimethyldioxirane (DMD), and m-chloroperbenzoic acid (mCPBA) by examining of the special structural and stereoelectronic features of the enecarbamates. Valuable mechanistic insight into these selective oxidations is gained. Whereas the R1 substituent on the chiral
手性恶唑烷酮取代enecarBAmates氧化的立体化学过程已经研究了单重态氧(1 Ò 2),二甲基二(DMD),和中号氯过苯甲酸(米通过的enecarBAmates的特殊的结构和立体电子特征检查CPBA) 。获得了对这些选择性氧化的有价值的机理见解。而手性助剂上的R 1取代基负责双键的空间屏蔽,并决定π面非对映选择性的感觉,Z / E构型等结构特征和R 2的性质双键上的基团负责非对映选择性的程度。在1 O 2的情况下,通过乙烯基氮官能团进行的立体电子控制可控制模式选择性(烯反应与[2 + 2]环加成反应)。
Construction of a quaternary carbon center via cyclic sulfite
作者:Nanae Nishimura、Oyo Mitsunobu
DOI:10.1016/s0040-4039(00)00315-4
日期:2000.4
Reaction of (S)-2-oxo-4-methyl-4-phenyl-1,3,2-dioxathiolane with triethylaluminum selectively took place at the tertiarycarbinol center to give (R)-2-methyl-2-phenyl-1-butanol. Enhanced stereoselectivity was obtained in a nonpolar solvent. Similarly, a series of (S)-4,4-disubstituted-1,3,2-dioxathiolanes reacted with trimethylaluminum to afford the corresponding (R)-2-alkyl-2-phenyl-1-propanols in
Resolution of Diols via Catalytic Asymmetric Acetalization
作者:Ji Hye Kim、Ilija Čorić、Chiara Palumbo、Benjamin List
DOI:10.1021/ja512481d
日期:2015.2.11
A highly enantioselective kinetic resolution of diols via asymmetricacetalization has been achieved using a chiral confined imidodiphosphoric acid catalyst. The reaction is highly efficient for the resolution of tertiary alcohols, giving selectivity factors of up to >300. Remarkably, even in cases where the selectivity factors are only moderate, highly enantioenriched diols are obtained via a stereodivergent
Camphor-derived 2-stannyl-N-Boc-1,3-oxazolidine: A new chiral formylanion equivalent for the asymmetric synthesis of 1,2-diols
作者:Lino Colombo、Marcello Di Giacomo、Gloria Brusotti、Ettore Milano
DOI:10.1016/0040-4039(95)00369-n
日期:1995.4
3-oxazolidine 6, prepared from the camphor-derived aminoalcohol 5, was converted to diastereomerically pure 2-acyl derivatives 8 in three steps. Reaction of these ketones with Grignard reagents at −78°C proceeded with high stereoselectivity affording tertiarycarbinols which gave 1,2-diols with >96% ee after hydrolysis and reduction of the intermediate α-hydroxy aldehydes. A new deblocking procedure of the