A practical and efficient method for enantioselective allylation of aldehydes
作者:E. J. Corey、Chan Mo Yu、Sung Soo Kim
DOI:10.1021/ja00196a082
日期:1989.7
La reaction d'(allyl-2 diphenyl-4,5 ditosyl-1,3)diazaborolidines-1,3,2 chirales avec des aldehydes fournit des alcools homoallyliques de maniere enantioselective
La 反应 d'(allyl-2 diphenyl-4,5 ditosyl-1,3)diazaborolidines-1,3,2 手性 avec des aldehydes Fournit des alcools homoallyliques de maniere enantioselective
Enantioselective synthesis using diisopropyl tartrate modified (E)- and (Z)-crotylboronates: Reactions with achiral aldehydes
作者:William R. Roush、Kaori Ando、Daniel B. Powers、Ronald L. Halterman、Alan D. Palkowitz
DOI:10.1016/s0040-4039(00)80816-3
日期:1988.1
The reactions of diisopropyl tartrate modified( E)- and (Z)-crotylboronates with representative achiral aldehydes are described. Enantioselectivity ranges from 55–91% e.e. depending on the aldehyde employed.
Diastereoselective Chain-Elongation Reactions Using Microreactors for Applications in Complex Molecule Assembly
作者:Catherine F. Carter、Heiko Lange、Daiki Sakai、Ian R. Baxendale、Steven V. Ley
DOI:10.1002/chem.201003148
日期:2011.3.14
Diastereoselective chain‐elongation reactions are important transformations for the assembly of complex molecular structures, such as those present in polyketide natural products. Here we report new methods for performing crotylation reactions and homopropargylation reactions by using newly developed low‐temperature flow‐chemistry technology. In‐line purification protocols are described, as well as
SYNTHESIS OF (S,S)-DIISOPROPYL TARTRATE (E)-CROTYLBORONATE AND ITS REACTION WITH ALDEHYDES: (2R,3R,4R)-1,2-DIDEOXY-2-ETHENYL-4,5-O-(1-METHYLETHYLIDENE)-XYLITOL
作者:Sun, Huikai、Roush, William R.
DOI:10.15227/orgsyn.088.0181
日期:——
N,N'-Bis(2,2,2-trifluoroethyl)-N,N'-ethylenetartramide: An Improved Chiral Auxiliary for the Asymmetric Allylboration Reaction
作者:William R. Roush、Paul T. Grover
DOI:10.1021/jo00117a036
日期:1995.6
N,N-Bis(2,2,2-trifluoroethyl)-N,N'-ethylenetartramide (8), synthesized by a simple four-step sequence from ethylenediamine and benzylidenetartaric acid, was designed in anticipation that the derived allylboronates 9-11 would display enhanced reactivity owing to the inductive effect of the N-trifluoroethyl substituents that would increase the Lewis acidity of the boron atom of the B-allyl-1,3,2-dioxaborolanes. Reagents 9-11 were synthesized by transesterification of 8 with the crystalline and easily purified allylboronate diethanolamine complexes 13, 19, and 25. Allylboronate 9 is ca. 100-fold more reactive than 6 and is also substantially more useful than the previously reported allyboronate 4, which suffers from very poor solubility in toluene at -78 degrees C. Most importantly, allylboronates 9-11 are significantly more enantioselective than the parent tartrate allylboronates 1-3 and rank among the most highly enantioselective allylboron reagents yet reported. Reactions of 9-11 with aldehydes are performed in THF at- -78 or -55 degrees C for 5-12 h periods. The enantioselectivity realized in reactions with achiral aldehydes is 92-95% ee (Table 2), and excellent diastereoselectivity is achieved in double asymmetric reactions with chiral aldehydes 15a, 15b, and 33 (Tables 3 and 4). For example, 16 and 28 are now available with a minimum selectivity of 92% from reactions of 15a and 15b with allylboronate 9, while the crotylboration products 29, 30, and 31 are available with a minimum selectivity of 90% (usually greater than or equal to 95%) from reactions of 15a and 15b with crotylboronates 10 and 11; the fourth isomer, 32a, is available with 83% selectivity. Chiral reagents 9-11 thus appear well suited for application to complex problems in organic synthesis.