Chiral bicyclic guanidines: a concise and efficient aziridine-based synthesis
作者:Weiping Ye、Dasheng Leow、Serena Li Min Goh、Chin-Tong Tan、Chee-Hoe Chian、Choon-Hong Tan
DOI:10.1016/j.tetlet.2005.11.133
日期:2006.2
series of chiral bicyclicguanidines, either symmetrical or non-symmetrical, was synthesized using a concise and efficient aziridine-based synthetic methodology. Starting from commercial amino alcohols, five synthetic steps were performed, with only three requiring chromatographic purification, giving the desired guanidines in 43–71% overall yield. Preliminary studies using these guanidines showed moderate
The organocatalytic Michael addition of malonates to symmetric unsaturated1,4-diketones catalyzed by thiourea and squaramide derivatives with Cinchona alkaloids afforded the formation of a new C-C bond in high yields (up to 98%) and enantiomeric purities (up to 93%). The absolute configuration of the product was suggested from comparison of the experimental and calculated VCD spectra of the reaction
1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed Michael reactions
作者:Weiping Ye、Junye Xu、Chin-Tong Tan、Choon-Hong Tan
DOI:10.1016/j.tetlet.2005.08.010
日期:2005.10
1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), a bicyclic guanidine base, has been found to be an excellent catalyst for Michael and Michael-type reactions. A wide variety of Michael donors and acceptors can participate in these reactions using 10-20 mol% of TDB. These reactions are mild, fast, easy to perform, produce excellent yields and can occur in several solvents without the need for strictly anhydrous conditions. (c) 2005 Elsevier Ltd. All rights reserved.
CaCl<sub>2</sub>, Bisoxazoline, and Malonate: A Protocol for an Asymmetric Michael Reaction
A mild protocol for the asymmetric Michael addition of dimethyl malonate to various alpha,beta-unsaturated carbonyl compounds was developed. The salient feature of this methodology is that a cheap and environmentally friendly Lewis acid, CaCl2, was used as a catalyst. An aminoindanol- and pyridine-derived ligand provided in the presence of CaCl2 Michael adducts in moderate to high enantioselectivities. The scope of the reaction was demonstrated.
Photosensitized Oxidation of Furans; VIII<sup>1</sup>. 3a,6a-Dihydrofuro[2,3-<i>b</i>] furan-2(3<i>H</i>)-ones, a New Class of Furo[2,3-<i>b</i>]furans