High-Pressure Enantioselective Allylation of Aldehydes Catalyzed by (Salen)Chromium(III) Complexes
作者:Janusz Jurczak、Piotr Kwiatkowski
DOI:10.1055/s-2004-836067
日期:——
The enantioselective addition of allyltributyltin to simple aldehydes (2a-1), catalyzed by chiral (salen)Cr(III) complexes 1, has been studied. The reaction proceeds smoothly with low loading (1-2 mol%) of (salen)Cr(III)BF 4 (la) and allyltributyltin under high-pressure conditions (10 kbar) in good yield and ee values in the range of 35-79%.
An Evans−Tishchenko−Ring-Closing Metathesis Approach to Medium-Ring Lactones
作者:Jennifer I. Aird、Alison N. Hulme、John W. White
DOI:10.1021/ol062932z
日期:2007.2.1
approach to the synthesis of medium-ring lactones is reported based on sequential Evans-Tishchenko and ring-closingmetathesis (RCM) reactions. High diastereoselectivity (>95:5) is demonstrated in the Evans-Tishchenko reaction of unsaturated aldehydes with unsaturated beta-hydroxy ketones, and conditions for the RCM cyclization of the resultant dienes have been optimized to give high yields of medium
A class of compounds useful in pharmaceutical compositions and methods for treating or preventing cancer is described. Analogs of Mycalolide B have been prepared and tested in breast and ovarian cancer cell lines. The compounds show utility for inhibition of survival and proliferation of tumor cells. The compounds have been shown to disrupt actin.
aldehydes, catalyzed by chiral (salen)Cr(III) complexes, has been studied. The reaction proceeded smoothly for the reactive 2-oxoaldehydes and allyltributyltin in the presence of small amounts (1–2 mol %) of (salen)Cr(III)BF4 (1b) under mild, undemanding conditions. However, in the case of other simple aldehydes, the use of high-pressure conditions is required to obtain good yields. Classic chromium catalyst
Catalytic Asymmetric Allylation of Aldehydes and Related Reactions with Bis(((S)-binaphthoxy)(isopropoxy)titanium) Oxide as aμ-Oxo-Type Chiral Lewis Acid
ee. This asymmetric allylation with non-racemic bis-Ti(IV) oxide 3 and partially resolved (S)-BINOL shows a positive nonlinear effect in correlation of the enantiopurity of the allylation product with the ee of the (S)-BINOL. Chiral bis-Ti(IV) oxide (S,S)-3 can also be utilized for related reactions such as asymmetric methallylation and propargylation of aldehydes with high enantioselectivity. This asymmetric