A practical procedure of low valent tin mediated Barbier allylation of aldehydes in wet solvent
摘要:
Use of aluminium as the reducing metal in spontaneous bimetal redox reaction has been elegantly exploited for allylation/crotylation of aldehydes in wet solvent. Here, low valent tin was prepared in situ by reduction of SnCl2 center dot 2H(2)O with aluminium in THF/water. The resulting low valent tin acted as an efficient mediator for allylation and crotylation of aldehydes (3a-q) producing the corresponding homoallylic alcohols. The efficacy of this procedure was due to its operational simplicity, practical viability, inexpensiveness, good yields of the products and short reaction time. (C) 2013 Elsevier Ltd. All rights reserved.
The Barbier‐type allylation of aldehydes and ketones can be carried out with both unsubstituted and γ‐substituted allyl bromides using only a catalytic amount (0.1 equiv.) of In metal in [bmim][Br].
An efficient synthesis of (-)-prelactone B has been developed using 1,2-cyclohexylidene glyceraldehyde as the chiral template. The key features of the synthesis were stereoselective crotylation of 1,2-cyclohexylidene glyceraldehyde and enantioselective reduction of a ketone, as well as operational simplicity and use of inexpensive reagents/chemicals.
A facile asymmetric synthesis of the octalactinlactone was developed staring from (R)-cyclohexylideneglyceraldehyde (1). The key step of the synthesis is an In-mediated diastereoselective crotylation of 1 in water, which furnished the building blocks with the required stereochemistry under operationally simple conditions. Their conversion to the appropriate intermediates, invertive esterification
a representative example of chiral β,γ-disubstituted-γ-butyrolactones. In this endeavor, crotylations of 1 in THF mediated with four low valent metals were studied. All these reactions took place efficiently producing 2 in good yields but with varied stereoselectivities. Each reaction produced the corresponding secondary alcohol adduct 2b and 2c predominantly with diastereoisomer 2a only in trace amounts
(<i>R</i>)-2,3-<i>O</i>-Cyclohexylideneglyceraldehyde, a Versatile Intermediate for Asymmetric Synthesis of Homoallyl and Homopropargyl Alcohols in Aqueous Medium
作者:Angshuman Chattopadhyay
DOI:10.1021/jo9604696
日期:1996.1.1
Zn-mediated allylation and propargylation of (R)-2,3-O-cyclohexylideneglyceraldehyde (1) in aqueous medium following Luche's procedure afforded the anti homoallylic 3 and homopropargylic 8 alcohols in good yield and with high stereoselectivity, Crotylation of 1 under similar conditions afforded appreciable amounts of erythro-5 and threo-6 alcohols. In each case, the diastereo alcohols are separable by column chromatography. Compound 8 on appropriate chemical manipulation of its functionalities gave the (S)-enantiomer of (R)-13, a useful synthon of LTB(4). Compound 3 on chemical elaboration afforded a diversely functionalized triol derivative 15, a potentially useful synthon for many bioactive compounds.