We report herein that the conjugate reduction of α,β-unsaturated esters and amides, such as aryl acrylates, pantolactone esters of acrylic acids, diethyl itaconate and N-crotonylcamphorsultam, with tributyltinhydride proceeded in moderate to high yields in the presence of magnesium bromide diethyl etherate. The effect of metal halide enhancing the yields is also described.
Na2CO3-Catalyzed O-Acylation of Phenols for the Synthesis of Aryl Carboxylates with Use of Alkenyl Carboxylates
作者:Xiao-Yu Zhou、Xia Chen
DOI:10.1055/s-0037-1610265
日期:2018.10
phenol and its derivatives has been developed. The procedure provides an efficient catalysis system for the preparation of aryl carboxylates with alkenyl carboxylates as acyl reagents. The reaction proceeded smoothly by using Na2CO3 as the catalyst in MeCN to produce the corresponding aryl carboxylates in good to excellent yields.
Asymmetric Cycloadditions of <i>o</i>-Quinone Methides Employing Chiral Ammonium Fluoride Precatalysts
作者:Ethan Alden-Danforth、Michael T. Scerba、Thomas Lectka
DOI:10.1021/ol802029e
日期:2008.11.6
The catalytic, enantioselective, [4 + 2] cycloaddition reaction of ortho-quinone methides with silyl ketene acetals is described. This mechanistically interesting reaction, initiated by a chiral cinchona alkaloid-derived ammonium fluoride "precatalyst" complex, affords a variety of alkyl- and aryl-substituted 3,4-dihydrocoumarin products in excellent yield and with good enantioselectivity.
A process is provided for the production of 6-hydroxy-2-naphthones, e.g., 6-hydroxy-2-acetonaphthone, by contacting a 2-naphthyl carboxylate ester, e.g., 2-naphthyl acetate with at least 20 moles of hydrogen fluoride per mole of 2-naphthyl ester, at reaction temperatures, e.g., 0 to 100° C for a period of reaction, e.g., 30 minutes to 8 hours sufficient to produce the desired amount of 6-hydroxy-2-naphthone. The process may utilize a carboxylic acid or anhydride, e.g., acetic acid or anhydride as an additive for the purpose of further increasing the regioselectivity of the 6-hydroxy-2-naphthone product. The process is capable of being carried out at a conversion of 2-naphthyl ester of at least 90% and a regioselectivity to 6-hydroxy-2-naphthone of at least 90 mol %.
A process is described for stereospecifically hydrating crotonobetaine to L-(-)-carnitine via the action of an enzyme produced by four new strains of Proteus mirabilis (NRRL B-18480, NRRL B-18481, NRRL B-18482, and NRRL B-18483) in biotransformation media containing from 10 to 12% (w/v) crotonobetaine inner salt.