An efficient synthesis of both enantiomers of chiral non racemic methylsulfoxides from DAG
摘要:
Diacetone-D-Glucose is stereoselectively converted to its (S)- or (R)-methanesulfinates 1 and 2 in 90 and 87% yield by treatment with methylsulfinyl chloride in the presence of diisopropylethylamine or pyridine, respectively. After purification, sulfinates 1 and 2 were transformed into both epimers of enantiomerically pure methylsulfoxides by reaction with Grignard reagents.
the use of different boronic acids, five-, six-, and seven-membered cyclic enones, an unsaturated lactone, and the most challenging acyclic ketones, is reported. An X-ray diffraction study of the [Ferbisox·RhCl]2 precatalyst clearly exhibits a dimeric structure with an S coordination of the sulfoxide to rhodium. On the basis of the X-ray data and on structural studies conducted in solution by 1H NMR
报道了无环C 2对称螯合双亚砜配体在Rh(I)催化的硼酸对电子缺陷烯烃的1,4-加成中的应用。在测试的无环乙烷桥联双亚砜中,配体Ferbisox(11),在亚磺酰基硫基上带有二茂铁基部分作为取代基,在化学收率(最高96%)和对映选择性(最高97%ee)方面表现出最好的结果。室温下,在短时间内(通常为2小时),在甲苯中平稳地进行共轭物加成。据报道,反应范围包括使用不同的硼酸,五元,六元和七元环状烯酮,不饱和内酯和最具挑战性的无环酮。[Ferbisox·RhCl] 2预催化剂的X射线衍射研究清楚显示出亚砜与铑具有S配位的二聚结构。根据X射线数据和在溶液中由1进行的结构研究提出了1 H NMR,其解释了观察到的高对映体的模型。
“Sulfolefin”: Highly modular mixed S/Olefin ligands for enantioselective Rh-catalyzed 1,4-addition
Reported is a single high yielding step approximation to mixed olefin/sulfinamide ligands enclosing a chiral sulfur atom as the sole chiral center. The synthetic design is validated by a rapid optimization of the substituent at the sulfinyl sulfur, and by the synthesis of an efficient, highly enantioselective catalyst for the Rh-catalyzed 1,4-addition of boronic acids to both, cyclic and acyclic olefins
New 2-alkylsulfinyl dithioacetates and thioacetamides have been prepared. The asymmetric synthesis of (R)-2-(cyclohexylsulfinyl)-N,N-dimethylthioacetamide from previously unreported (S)-diacetone-d-glucose cyclohexanesulfinate was achieved in excellent yield (91%) and enantiomeric excess (98%). Methyl (R)-2-(cyclohexylsulfinyl)dithioacetate (98% ee) was obtained from chiral cyclohexyl methyl sulfoxide (99% ee).
Various chiral secondary alcohols have been used to study the dependence of the stereochemical outcome of sulfinate and phosphinate ester synthesis on the nature of the base used to catalyse the reaction. From this study it has been shown that the achiral stereodirecting base effect determined in the DAG methodology is a general behaviour in the asymmetricsynthesis of sulfinate and phosphinate esters
Dynamic Kinetic Transformation of Sulfinyl Chlorides: Synthesis of Enantiomerically Pure <i>C</i><sub>2</sub>-Symmetric Bis-Sulfoxides
作者:Noureddine Khiar、Cristina S. Araújo、Felipe Alcudia、Inmaculada Fernández
DOI:10.1021/jo0159183
日期:2002.1.1
the synthesis of both isomers of a large number of optically pure C(2)-symmetric bis-sulfoxides have been developed, and their scope and limitations have been assessed. The first one uses as intermediate diastereomerically pure C(2)-symmetric bis-sulfinate esters 6(S(S),S(S)) and 6(R(S),R(S)), obtained by dynamic kinetic resolution of ethane-1,2-bis-sulfinyl chloride 5. A single inducer of chirality