A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of Benzo-Substituted Cyclopentenones
摘要:
A new annulation sequence leading to benzo-substituted cyclopentenones is effected by treating o-alkynyl-substituted alpha-diazoacetophenones containing tethered heteroatoms with Rh(II) carboxylates. The reaction involves addition of the initially formed keto carbenoid onto the acetylenic pi-bond to give a rearranged vinyl carbenoid. Sulfonium ylide formation occurred both intra- and intermolecularly when the reaction was carried out in the presence of a sulfide. In the case where an ether oxygen was present on the backbone of the vinyl carbenoid, the resulting oxonium ylide underwent a [1,2]- or [2,3]-shift to give the rearranged product. These cyclic metallocarbenoids were also found to interact with a neighboring carbonyl or oximino pi-bond to produce carbonyl or azomethine ylides. The 1,3-dipoles generated in this manner were trapped with dimethyl acetylenedicarboxylate. The domino transformation was also performed intramolecularly by attaching a trapping agent directly to the carbonyl group. Incorporation of an amido carbonyl on the alkyne side chain was found to dramatically alter the course of the tandem annulation reaction. A novel rearranged cycloadduct was formed in high yield whose structure was elucidated by X-ray crystallography. The mechanism for its formation involves the opening of a transient intermediate oxabicyclo[2.2.1]heptane followed by a Wagner-Meerwein rearrangement.
A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of Benzo-Substituted Cyclopentenones
摘要:
A new annulation sequence leading to benzo-substituted cyclopentenones is effected by treating o-alkynyl-substituted alpha-diazoacetophenones containing tethered heteroatoms with Rh(II) carboxylates. The reaction involves addition of the initially formed keto carbenoid onto the acetylenic pi-bond to give a rearranged vinyl carbenoid. Sulfonium ylide formation occurred both intra- and intermolecularly when the reaction was carried out in the presence of a sulfide. In the case where an ether oxygen was present on the backbone of the vinyl carbenoid, the resulting oxonium ylide underwent a [1,2]- or [2,3]-shift to give the rearranged product. These cyclic metallocarbenoids were also found to interact with a neighboring carbonyl or oximino pi-bond to produce carbonyl or azomethine ylides. The 1,3-dipoles generated in this manner were trapped with dimethyl acetylenedicarboxylate. The domino transformation was also performed intramolecularly by attaching a trapping agent directly to the carbonyl group. Incorporation of an amido carbonyl on the alkyne side chain was found to dramatically alter the course of the tandem annulation reaction. A novel rearranged cycloadduct was formed in high yield whose structure was elucidated by X-ray crystallography. The mechanism for its formation involves the opening of a transient intermediate oxabicyclo[2.2.1]heptane followed by a Wagner-Meerwein rearrangement.
Rhodium(II)-catalyzed cyclization reactions of alkynyl-substituted .alpha.-diazo ketones
作者:Albert Padwa、Keith E. Krumpe、Yves Gareau、Ugo Chiacchio
DOI:10.1021/jo00007a047
日期:1991.3
Treatment of several omicron-alkynl-substituted alpha-diazoacetophenone derivatives with rhodium (II) carboxylates results in the formation of substituted indenones. The simplest mechanism accounting for the results involves addition of a rhodium-stabilized carbenoid onto the acetylenic pi-bond to generate a vinyl carbenoid directly of possibly a highly strained cyclopropene derivative. The vinyl carbenoid was found to undergo addition to a neighboring alkene tethered on the side chain to give an indenyl-substituted bicyclo[3.1.0]hexane derivative. A number of related systems were examined so as to probe the scope and generality of the process. Treatment of omicron-(6,8-nonadien-1-ynyl)-alpha-diazoacetophenone with rhodium (II) mandelate afforded a cyclopent[g]azulenone derivative. The formation of this compound involves a divinylcyclopropane intermediate that readily undergoes a Cope rearrangement under the reaction conditions. The rhodium-catalyzed reaction of 2-(6-oxo-1-hepty-nyl)-alpha-diazoacetophenone in the presence of N-phenylmaleimide afforded a mixture of two cycloadducts. One of the products can be accounted for in terms of a cyclization of the vinyl carbenoid onto the oxygen atom of the neighboring carbonyl group to give a resonance-stabilized dipole. 1,3-Dipolar cycloaddition of the carbonyl ylide across the activated pi-bond of N-phenylmaleimide affords the observed product. The second cycloadduct is formed by a 1,2-hydrogen shift of the initially produced vinyl carbenoid. The resulting diene undergoes a subsequent Diels-Alder reactions with N-phenylmaleimide.
PADWA, ALBERT;KRUMPE, KEITH E.;GAREAU, YVES;CHIACCHIO, UGO, J. ORG. CHEM., 56,(1991) N, C. 2523-2530
作者:PADWA, ALBERT、KRUMPE, KEITH E.、GAREAU, YVES、CHIACCHIO, UGO
DOI:——
日期:——
A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of Benzo-Substituted Cyclopentenones
作者:Albert Padwa、Jamal M. Kassir、Mark A. Semones、M. David Weingarten
DOI:10.1021/jo00106a014
日期:1995.1
A new annulation sequence leading to benzo-substituted cyclopentenones is effected by treating o-alkynyl-substituted alpha-diazoacetophenones containing tethered heteroatoms with Rh(II) carboxylates. The reaction involves addition of the initially formed keto carbenoid onto the acetylenic pi-bond to give a rearranged vinyl carbenoid. Sulfonium ylide formation occurred both intra- and intermolecularly when the reaction was carried out in the presence of a sulfide. In the case where an ether oxygen was present on the backbone of the vinyl carbenoid, the resulting oxonium ylide underwent a [1,2]- or [2,3]-shift to give the rearranged product. These cyclic metallocarbenoids were also found to interact with a neighboring carbonyl or oximino pi-bond to produce carbonyl or azomethine ylides. The 1,3-dipoles generated in this manner were trapped with dimethyl acetylenedicarboxylate. The domino transformation was also performed intramolecularly by attaching a trapping agent directly to the carbonyl group. Incorporation of an amido carbonyl on the alkyne side chain was found to dramatically alter the course of the tandem annulation reaction. A novel rearranged cycloadduct was formed in high yield whose structure was elucidated by X-ray crystallography. The mechanism for its formation involves the opening of a transient intermediate oxabicyclo[2.2.1]heptane followed by a Wagner-Meerwein rearrangement.