Solvent-free Mukaiyama aldol reaction of O-silyl dienolates catalyzed by benzoic acid
摘要:
The vinylogous aldol reaction of O-silyl dienolates deriving from 2,2-dimethyl-[1,3]-dioxin-4-ones proceeds in moderate to excellent yields in the presence of catalytic amounts of PhCOOH under solvent-free conditions. Modest to good yields can be obtained by using silica gel or 3 A molecular sieves as heterogeneous catalysts. (c) 2005 Elsevier Ltd. All rights reserved.
Stereoselective Synthesis of Tetrahydropyran-4-ones from Dioxinones Catalyzed by Scandium(III) Triflate
作者:William J. Morris、Daniel W. Custar、Karl A. Scheidt
DOI:10.1021/ol050093v
日期:2005.3.1
[reaction: see text] A scandium triflatecatalyzed, diastereoselective cyclization between aldehydes and beta-hydroxy dioxinones has been discovered. This process capitalizes on the untapped nucleophilicity of the embedded enol ether within the dioxinone core. The bicyclic compounds from the resulting cyclization can be isolated, or alternatively, alkoxide nucleophiles can be directly added. This in
Versatile Asymmetric Synthesis of the Kavalactones: First Synthesis of (+)-Kavain
作者:Thomas E. Smith、Mabel Djang、Alan J. Velander、C. Wade Downey、Kathleen A. Carroll、Sophie van Alphen
DOI:10.1021/ol0493960
日期:2004.7.1
Three asymmetric pathways to the kavalactones have been developed. The first method is chiral auxiliary-based and utilizes aldol reactions of N-acetyl thiazolidinethiones followed by a malonate displacement/decarboxylation reaction. The second approach uses the asymmetric catalytic Mukaiyama additions of dienolate nucleophile equivalents developed by Carreira and Sato. Finally, tin-substituted intermediates, prepared by either of these routes, can serve as advanced general precursors of kavalactone derivatives via Pd(0)-catalyzed Stille couplings with aryl halides.
Solvent-free Mukaiyama and Mukaiyama–Michael vinylogous reactions of a dioxinone-derived silyl enol ether promoted by Lewis bases
作者:Arrigo Scettri、Vincenzo De Sio、Rosaria Villano、Patrizia Manzo、Maria Rosaria Acocella
DOI:10.1016/j.tetlet.2010.05.016
日期:2010.7
The vinylogous aldol-type addition of a dienolsilyl ether, derived from 2,2,6-trimethyl-4H-1,3-dioxin-4-one, showed to occur with complete gamma-selectivity by enolate activation promoted by neutral Lewis bases under solvent-free conditions. Moderate to high yields were obtained with aromatic, hetero-aromatic, and aliphatic aldehydes, as well as activated ketones. Under the same conditions and in the absence of catalyst, the first Mukaiyama-Michael addition of the masked acetoacetate ester to alpha,beta-unsaturated aldehydes took place in satisfactory way. (C) 2010 Elsevier Ltd. All rights reserved.
Highly Stereoselective Brønsted Acid Catalyzed Synthesis of Spirooxindole Pyrans
作者:Jingqi Wang、Erika A. Crane、Karl A. Scheidt
DOI:10.1021/ol200987c
日期:2011.6.17
A Bronsted acid-catalyzed Prins-type cyclization sequence to construct spirooxindole pyrans in high yields and excellent diastereoselectivity has been developed. The combination of a beta-hydroxy dioxinone fragment and isatin dimethyl acetal generate oxa-spirooxindoles efficiently. These compounds are diversifiable scaffolds that tap into the rich chemistry of dioxinones.
Solvent-free Mukaiyama aldol reaction of O-silyl dienolates catalyzed by benzoic acid
The vinylogous aldol reaction of O-silyl dienolates deriving from 2,2-dimethyl-[1,3]-dioxin-4-ones proceeds in moderate to excellent yields in the presence of catalytic amounts of PhCOOH under solvent-free conditions. Modest to good yields can be obtained by using silica gel or 3 A molecular sieves as heterogeneous catalysts. (c) 2005 Elsevier Ltd. All rights reserved.