A novel visible-light-induced cascade reaction for the preparation of ester-functionalized polyheterocycles was developed under metal-free conditions, which was initiated by an intermolecular radical addition to a carbon-carbon double bond of N-arylacrylamide derivatives using alkyl carbazate as the ester source followed by cyano-mediated cyclization. The desired phenanthridine derivative products were isolated in moderate to high yields with broad substrate scope.
A formal 1,6-conjugated addition-mediated [2+1] annulation to synthesize spiro[2.5]octa-4,7-dien-6-one with p-quinone methides and sulfur ylides has been described. This domino-type process was highly diastereoselective and exhibited good functional group tolerance and scalability without the use of metals and bases.
An efficient one-pot approach for the synthesis of spiro[2.5]octa-4,7-dien-6-ones by employing para-quinone methides has been developed. The reaction proceeded smoothly in high yields under mild conditions without the use of metals. Moreover, all products obtained herein contained two or three consecutive quaternary centers.
A palladium-catalyzed remote 1,n-arylamination (from 1,3-to 1,11-arylamination) of unactivated terminal alkenes with aryl iodides and arylamines has been realized. This three-component reaction proceeded via Pd-catalyzed Heck arylation, alkene isomerization, and aza-Michael addition, exhibiting good regio-and chemoselectivity, and wide substrate scope. Preliminary mechanistic studies indicated that the in situ generated ortho/para-quinone methide intermediates served as the driving force for the alkene isomerization and promoted the rearomatization upon nucleophilic amination.
An
unprecedented acid- and ligand-controlled divergent allylation
of indoles with unactivated skipped enynes via Pd hydride catalysis
has been disclosed. This redox-neutral transformation went through
multiple hydropalladation insertion, β-hydrogen elimination,
π–σ–π isomerization, and allylic substitution
steps. This method not only provides a platform for synthesizing indolenines
and N-allylindoles but also allows facile access
to functional 1,3-dienes with high atom and step economy.
A palladium-catalyzed dearomative allylic alkylation of indoles with alkynes to construct indolenines with C3-quarternary centers was reported. The in situ formed arylallene intermediate omitted the need to install leaving groups on the allylic compounds and employ extra oxidants to oxidize the allylic C-H bonds. The reaction exhibited good functional group tolerance and high atom economy. Moreover, the reaction was further expanded to synthesize pyrroloindolines and furanoindolines.
A dearomative coupling of β-naphthols with alkynes via Pd hydride catalysis has been developed. This redox-neutral strategy provides a straightforward platform to access diverse naphthalenones bearing congested quarternary stereocenters with excellent atom and step economy since no leaving groups are needed to preinstall on the allylic reagents. The overall utility of this protocol is exemplified by broad functional group compatibility and gram-scale capacity.
Pd-catalyzed
sequential hydroamination of readily available 1,3-enynes
is reported. The redox-neutral process provides an efficient route
to synthesize a broad scope of imidazolidinones, thiadiazolidines,
and imidazolidines. Asymmetric sequential hydroamination generates
a series of synthetically valuable, enantioenriched imidazolidinones.
Mechanistic studies revealed that the transformation occurred via
an intermolecular enyne hydroamination pathway to give an allene intermediate.
Subsequent intramolecular hydroamination of the allene intermediate
proceeded under the Curtin–Hammett principle to provide enantioenriched
imidazolidinone products.
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