Sequential Morita–Baylis–Hillman/Achmatowicz reactions: an expeditious access to pyran-3(6H)-ones with a unique substitution pattern
摘要:
We herein disclosed a novel approach to synthesize densely functionalized 6-hydroxy-2H-pyran-3(6H)-ones with moderate to good diastereoselectivity. The method is based on a two step sequence using Morita-Baylis-Hillman adducts as substrates for the Achmatowicz rearrangement, allowing the preparation of highly substituted pyran-3-ones with overall yields ranging from 17% to 80% and a unique substitution pattern. (C) 2015 Elsevier Ltd. All rights reserved.
1,3,5-Triaza-7-phosphaadamantane (PTA): A Practical and Versatile Nucleophilic Phosphine Organocatalyst
作者:Xiaofang Tang、Bo Zhang、Zhengrong He、Ruili Gao、Zhengjie He
DOI:10.1002/adsc.200700071
日期:2007.8.6
cycloaddition reaction of 4-substituted 2,3-butadienoates with N-tosylimines, PTA is also proven to be a comparable catalyst as tributylphosphine (PBu3). By systematic comparison with other structurally similar N,P catalysts, it is concluded that the superiority of PTA in the above nucleophilic catalysis is attributable to its comparable nucleophilicity with that of trialkylphosphines. The feasibility
Baylis-Hillman Reaction
of Cyclic Enones with Arenecarbaldehydes and <i>N-</i>Arylidene-4-methylbenzenesulfonamides
by Using NAP-MgO
作者:M. Kantam、L. Chakrapani、B. Choudary
DOI:10.1055/s-2008-1077959
日期:——
Baylis-Hillman reaction of cyclic enones with arenecarbaldehydes and N-arylidene-4-methylbenzenesulfonamides under mild conditions by using nanocrystalline MgO (NAP-MgO) afforded the Baylis-Hillman adducts in moderate to good yields with higher selectivity than the corresponding aldol products.
An efficient and simple Morita–Baylis–Hillman reaction based on the N-methylpyrrolidine–Ba(OH)2 catalytic system
作者:Krassimira P. Guerra、Carlos A.M. Afonso
DOI:10.1016/j.tet.2011.02.020
日期:2011.4
By using of precise catalytic amount of N-methylpyrrolidine (5 mol %) and Ba(OH)2 (1.5 mol %) in H2O/CH3OH 5/1 or CH3OH/CH2Cl2 3/1 solvent mixtures at T=0 °C a Morita–Baylis–Hillman derivatives could be obtained in good to excellent yield from 2-cyclopenten-1-one, 2-cyclohexen-1-one and formaldehyde and diverse aryl aldehydes after suitable reaction time.
Tributylphosphine or dimethylphenylphosphine (1-5 mol%) catalyzed the Morita-Baylis-Hillman reaction of 2-cyclopenten-1-one (1) with 1.2 equivalents of formalin proceeded nicely to give 2-hydroxymethyl-2-cyclopenten-1-one (2) within a short period and in an excellent yield. The efficiency of the reaction (yield and time) was strongly dependent on the solvent and the best result was obtained in the case of an aqueous MeOH-CHCl3 solvent system.
Efficient Tandem Morita-Baylis-Hillman/Double Cross-Aldol Reaction between Cyclic Enones and Formaldehyde Promoted by N-Methylpyrrolidine
作者:Krassimira P. Guerra、Carlos A. M. Afonso
DOI:10.1002/ejoc.201001612
日期:2011.4
The Lewis base N-methylpyrrolidine acts in water as an efficient promoter of tandemreactionsbetween 2 cyclopenten-1-one and aqueous formaldehyde. The reaction pathway includes, as consecutive independent steps, a MBH reaction and a doublecross-aldolreaction to furnish the new 2,5,5-tris(hydroxymethyl)-2-cyclopenten-1-one in excellent yield. A range of cyclicenones and 4-nitrobenzaldehyde undergo