Microwave-assisted synthesis of the (E)-α-methylalkenoate framework from multifunctionalized allylic phosphonium salts
作者:Lidiane Meier、Misael Ferreira、Marcus M. Sá
DOI:10.1002/hc.21001
日期:——
A convenient and general microwave-assisted method for the synthesis of stereochemicallydefined α-methylalkenoic acids and esters from allylic phosphonium salts in a basic aqueous medium is described. A selective preparation of acids or esters was dependent on the base (NaOH or NaHCO3) employed in the reaction and could be achieved with good to excellent yields under mild conditions in the absence
[reaction: see text] In homogeneous H(2)O/solvent medium, the reactionrate of aromatic aldehydes and acrylonitrile or acrylate was greatly accelerated, which led to shorter reaction time, lower reaction temperature, and higher yield. In this reaction, Me(3)N, DMAP, DABCO, and urotropine were good catalysts. Except for low-carbon alcohols, tetrahydrofuran, 1,4-dioxane, and acetonitrile could be chosen
environmentally benign manner. A novel C–OH bond cleavage method was found to be crucial for this practical protocol. A variety of alkenes and allylic alcohols equipped with wide-spectrum functional groups can be successfully incorporated into the desired cross-coupling, affording 1,4-dienes with moderate to excellent yields and high stereo- and regioselectivity.
The halogen-bonded adduct between DABCO and two molecules of perfluorooctyl iodide (DABCO.(C(8)F(17)I)(2)) acts as a recyclable organocatalyst for the Morita-Baylis-Hillman reaction. This "supramolecular fluorous catalyst" is readily accessible and can be recovered by simple precipitation/filtration.
organic photoredox-catalyzed dehydroxylative trifluoromethylation of allylic alcohols was developed in an environmentally benign manner. In this reaction, the readily available CF3SO2Na was selected as the trifluoromethylation reagent. The in situ generated byproduct SO2 was reutilized to activate C–OH bond, which enabled this dehydroxylative trifluoromethylation to be performed conveniently. A variety
以环境友好的方式开发了有机光氧化还原催化的烯丙醇脱羟基三氟甲基化。本反应选用易得的CF 3 SO 2 Na作为三氟甲基化试剂。在原位通过产品生成SO 2被再利用来激活C-OH键,这使此dehydroxylative三氟甲基化将被方便地进行。以高产率和优异的立体选择性获得了多种多功能化的 CF 3 -烯丙基化合物。