A Copper(I)-Catalyzed Addition/Annulation Sequence for the Two-Component Synthesis of γ-Ylidenebutenolides
A highly efficient Cu(I)-catalyzed addition/annulation sequence has been developed for the synthesis of (Z)-ylidenebutenolides employing readily available α-ketoacids and alkynes as substrates. The reactions employ a simple commercially available Cu(I)-catalyst, display good substrate scope, and deliver products with high stereoselectivity. The synthetic utility of the method is demonstrated by the straightforward derivatization of the ylidenebutenolides into a diverse range of heterocycles, and also by the preparation of the natural product bovolide, and analogs thereof.
Seo, Sangwon,Willis, Michael C.
supporting information
p. 4556 - 4559
(2017/09/11)
Two-Step Synthesis of (Z)-3-Aryl-5-(arylmethylidene)butenolides by an Ivanov Reaction/Silver(I)-Catalyzed Lactonization/In Situ Dehydration Sequence
A stereoselective synthesis of the title compounds was developed. Hexane- and amine-free THF solutions of α-lithiated lithium arylacetates ('arylacetic acid dianions') were aldol-added to 3-arylpropynals. This gave 2,5-diaryl-3-hydroxypent-4-ynoic acids with up to a 72:28 preference for the anti-diastereomer (27 examples + 1 exception). When treated with Ag2CO3 (1-20 mol%) in DMF at room temperature for 2.5 days, the respective mixtures underwent regio- and stereoselective lactonizations followed by an in situ dehydration. Thereby 3-aryl-5-(arylmethylidene)butenolides were obtained with a Z-configuration of the oxygenated C=C bond. Their overall yields ranged from 46% to 83% (1 exception: 28%). Three 3-aryl-5-(arylmethylidene)butenolides contained a C-Br and/or a C-I bond. They allowed a subsequent Pd-catalyzed C-C coupling, which furnished follow-up butenolides.
Hermann, David,Arican, Deniz,Brückner, Reinhard
p. 326 - 352
(2016/12/24)
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