Topic
Annulation
About: Annulation is a research topic. Over the lifetime, 10152 publications have been published within this topic receiving 189701 citations.
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TL;DR: The protocol was successfully applied to the total synthesis of the natural product papaverine and showed good functional group tolerance.
75 citations
TL;DR: A polystyrene-supported isothiourea (1a) behaves as a highly efficient organocatalyst in a variety of formal [4 + 2] cycloaddition reactions.
Abstract: A polystyrene-supported isothiourea (1a) behaves as a highly efficient organocatalyst in a variety of formal [4 + 2] cycloaddition reactions. The catalytic system has proven to be highly versatile, leading to six-membered heterocycles and spiro-heterocycles bearing an oxindole moiety in high yields and very high enantioselectivities (32 examples, including the previously unreported oxindole spiropyranopyrazolones 8; 97% mean ee). The notable chemical stability of 1a under operation conditions results in high recyclability (11 cycles, accumulated TON of 76.8) and allows the implementation of an extended-operation continuous flow process (no decrease in yield or ee after 18 h).
75 citations
TL;DR: A new type of intermolecular (4 + 2) cycloaddition, based on a gold-catalyzed reaction between allenamides and acyclic conjugated dienes, is reported, which provides a straight entry to a variety of differently substituted cyclohexenes.
Abstract: A new type of intermolecular (4 + 2) cycloaddition, based on a gold-catalyzed reaction between allenamides and acyclic conjugated dienes, is reported. The annulation, which fails under standard Diels–Alder conditions, provides a straight entry to a variety of differently substituted cyclohexenes, and takes place with excellent regio- and diastereoselectivity.
75 citations
TL;DR: A novel, efficient, and facile vicinal sulfonamination of alkynes by the reaction of accessible 2-alkynyl arylazides with sulfinic acids in the presence of tert-butyl hydroperoxide has been developed.
75 citations
TL;DR: The preliminary mechanistic studies suggest that a CH cleavage is the rate-determining step and the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from α,β-unsaturated carboxylic acids and allenes.
Abstract: A highly regio- and stereoselective synthesis of 3,3-disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3-vinyl-substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from α,β-unsaturated carboxylic acids and allenes. The reactions proceed through a carboxylate-assisted ortho-CH activation and [4+1] annulation. The preliminary mechanistic studies suggest that a CH cleavage is the rate-determining step.
74 citations