An official website of the United States government
Abstract The direct synthesis of α‐sulfonyl ketones was accomplished by a multicomponent reaction of styrene derivatives, anilines,t‐butyl nitrite, 1,4‐diazabicyclo[2.2.2]octane‐sulfur dioxide (DABSO), and oxygen catalyzed by salicylic acid. The aryl radicals generated from aniline derivatives andt‐butyl nitrite under the catalysis of salicylic acid was sulfonylated by DABSO to generate the arylsulfonyl radicals, which reacted further with styrenes, and then oxidized by oxygen to give the title compounds. Under the optimized conditions, the title compounds were obtained in good yields at ambient temperature within 1.5–2 h.
more »
« less
Strain‐Induced Nucleophilic Ring Opening of Donor–Acceptor Cyclopropenes for Synthesis of Monosubstituted Succinic Acid Derivatives
Abstract 1,2,3‐Trisubstituted donor–acceptor cyclopropenes (DACPs) generated in situ from enoldiazo compounds react with nucleophiles to form α‐substituted succinic acid derivatives in high yields. Initial dirhodium(II) carboxylate catalysis rapidly converts enoldiazo‐acetates or ‐acetamides to DACPs that undergo catalyst‐free Favorskii ring opening with amines, and also with anilines, alcohols, and thiols, when facilitated by catalytic amounts of 4‐dimethylaminopyridine (DMAP). This methodology provides easy access to mixed esters and amides of monosubstituted succinic acids, including derivatives of naturally occurring compounds. It also affords dihydrazide, dihydroxamic acid, and diamide derivatives, as well as α‐substituted tetrahydropyridazine‐3,6‐diones in high yields. Attempts to generate optically enriched DACPs were not successful because their populations having theRandSconfigurations formed with a chiral dirhodium catalyst are quite similar, and the loss of enantiocontrol likely originates from the DACP ring forming step which is reversible with its intermediate metal carbene.
more »
« less
- Award ID(s):
- 1763168
- PAR ID:
- 10237070
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 27
- Issue:
- 1
- ISSN:
- 0947-6539
- Page Range / eLocation ID:
- p. 340-347
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Chiral copper( i ) catalysts are preferred over chiral dirhodium( ii ) catalysts for [3 + 3]-cycloaddition reactions of γ-alkyl-substituted enoldiazoacetates compounds with nitrones. Using the In-SaBox ligand these reactions effectively produce cis -3,6-dihydro-1,2-oxazine derivatives under mild conditions in high yield and with exceptional stereocontrol, and enantioselectivity increases with the size of the γ-substituent. Mechanistic studies show that cycloaddition occurs solely through the formation of ( Z )-γ-substituted metallo-enolcarbene intermediates that are catalytically gennerated from both ( Z )- and ( E )-γ-substituted enoldiazoactates via donor–acceptor cyclopropene intermediates.more » « less
-
Abstract The direct Friedel–Crafts‐type coupling and dedinitrogenation reactions of vinyldiazo compounds with aromatic compounds using a metal‐free strategy are described. This Brønsted acid catalyzed method is efficient for the formation of α‐diazo β‐carbocations (vinyldiazonium ions), vinyl carbocations, and allylic or homoallylic carbocation species via vinyldiazo compounds. By choosing suitable nucleophilic reagents to selectively capture these intermediates, both trisubstituted α,β‐unsaturated esters, β‐indole‐substituted diazo esters, and dienes are obtained with good to high yields and selectivity. Experimental insights implicate a reaction mechanism involving the selective protonation of vinyldiazo compounds and the subsequent release of dinitrogen to form vinyl cations that undergo intramolecular 1,3‐ and 1,4‐ hydride transfer processes as well as fragmentation.more » « less
-
Abstract A Brønsted acid catalyzed C–H functionalization of vinyldiazoacetates with 3-hydroxyisoindolinone is developed. This methodology provides a general access to E-substituted isoindolinone vinyldiazo compounds in good yields and excellent diastereoselectivities with broad substrate generality under mild conditions, and with 4-substituted 2-diazo-3-butenoates produces fused bicyclic pyrrolidines. The reaction generally involves addition of the N-acyl ketiminium electrophile, formed from the 3-hydroxyisoindolinone, to the vinylogous position of the vinyldiazo compound resulting in vinyldiazonium ion intermediates that undergo deprotonation to new vinyldiazo compounds or ring closure to fused bicyclic pyrrolidines.more » « less
-
Abstract A transition metal‐free Se‐catalyzed C−H amination protocol for α’‐amination of enol derivatives has been developed. This reaction can be used to functionalize a wide variety of oxygen‐ and halogen‐substituted alkenes spanning a vast range of nucleophilicities, giving α’‐aminated enol derivatives with high regioselectivity. Amination ofE/Zmixtures of alkenes proceeds stereoconvergently to give the (Z)‐enol derivatives exclusively. Mechanistic studies revealed that the relative reactivity and α’‐regioselectivity of these transformations is determined by substantial resonance donation to the heteroatom‐bound carbon in the transition state. These products participate in traditional reactions of enol derivatives, allowing for efficient functionalization of both α‐ and α’‐positions from a single enol derivative with high diastereocontrol.more » « less
