- Claisen-type condensation of vinylogous acyl triflates
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(Chemical Equation Presented) The Claisen-type condensation reaction of cyclic vinylogous carboxylic acid triflates with lithium enolates and their analogues produces acyclic alkynes bearing a 1,3-diketone-type moiety. The present transformation is proposed to proceed via a 1,2-addition of the enolate to the vinylogous acyl triflate, followed by fragmentation of the aldolate intermediate.
- Kamijo, Shin,Dudley, Gregory B.
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- Ring opening of cyclic vinylogous acyl triflates using stabilized carbanion nucleophiles: Claisen condensation linked to carbon-carbon bond cleavage
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Addition of stabilized carbanionic nucleophiles to cyclic vinylogous acyl triflates (VATs) triggers a ring-opening fragmentation to give acyclic β-keto ester and related products, much like those observed traditionally in the Claisen condensation. Unlike in the classical Claisen condensation, however, the VAT-Claisen reaction described herein is rendered irreversible by C-C bond cleavage, not by deprotonation of the activated methylene product. Full details of this original reaction methodology are disclosed herein, including how subtle differences between the various nucleophiles impact the proper choice of reaction conditions for making 1,3-diketones, β-keto esters, and β-keto phosphonates.
- Jones, David M.,Lisboa, Marilda P.,Kamijo, Shin,Dudley, Gregory B.
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experimental part
p. 3260 - 3267
(2010/08/19)
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- Tandem nucleophilic addition/fragmentation reactions and synthetic versatility of vinylogous acyl triflates
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A thorough analysis of the chemistry of vinylogous acyl triflates provides insight into important chemical processes and opens new directions in synthetic technology. Tandem nucleophilic addition/C-C bond cleaving fragmentation reactions of cyclic vinylogous acyl triflates 1 yield a variety of acyclic acetylenic compounds. Full details are disclosed herein. A wide array of nucleophiles, such as organolithium and Grignard reagents, lithium enolates and their analogues, hydride reagents, and lithium amides, are applied. The respective reactions produce ketones 2, 1,3-diketones and their analogues 3, alcohols 4, and amides 5. The present reactions are proposed to proceed through a 1,2-addition of the nucleophile to the carbonyl group of starting triflates 1 to form tetrahedral alkoxide intermediates C, followed by Grob-type fragmentation, which effects C-C bond cleavage to yield acyclic acetylenic compounds 2-5 and 7. The potent nucleofugacity of the triflate moiety is channeled through the σ-bond framework of 1, providing direct access to the fragmentation pathway without denying other typical reactions of cyclic vinylogous esters. The synthetic versatility of vinylogous acyl triflates, including functionalization reactions of the cyclic enone core (1 → 6 or 8), is also illustrated.
- Kamijo, Shin,Dudley, Gregory B.
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p. 6499 - 6507
(2007/10/03)
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- Control of the Regioselectivity of Oxidative Free-Radical Cyclizations by Addition to Haloalkenes
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Chlorine substituents on the alkene control the regioselectivity of the cyclization of 5-hexenyl or 6-heptenyl radicals generated by oxidation of an acetoacetate ester or 1,3-diketone with Mn(OAc)3*2H2O. 6-Exo-cyclization of the radicals obtained by oxida
- Snider, Barry B.,Zhang, Qingwei,Dombroski, Mark A.
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p. 4195 - 4205
(2007/10/02)
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