@article {42449, title = {Arynes in transition-metal-free multicomponent coupling reactions}, journal = {Angewandte Chemie-International Edition}, volume = {51}, year = {2012}, month = {FEB}, pages = {1520{\textendash}1522}, abstract = {

Let{\textquoteright}s couple together! The multicomponent reactions involving arynes offer direct access to unusual heterocyclic scaffolds and 1,2-disubstituted arenes. This transition-metal-free, one-pot construction of molecular complexity is likely to play a pivotal role in various carbon{\textendash}carbon and carbon{\textendash}heteroatom bond-forming reactions.

}, doi = {10.1002/anie.201106984}, author = {Bhojgude, Sachin Suresh and Biju, Akkattu T.} } @article {42446, title = {Efficient diels-alder reaction of 1,2-benzoquinones with arynes and its utility in one-pot reactions}, journal = {Organic Letters}, volume = {14}, year = {2012}, month = {DEC}, pages = {6238{\textendash}6241}, abstract = {

A new protocol for the efficient Diels{\textendash}Alder reaction of 1,2-benzoquinones with arynes is reported. The aryne generated by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes a facile Diels{\textendash}Alder reaction with 1,2-benzoquinones, affording the dioxobenzobicyclooctadienes in moderate to excellent yields. In addition, this methodology has been applied to the one-pot synthesis of benzoquinoxalinobarrelene and naphthalene derivatives.

}, doi = {10.1021/ol302997q}, author = {Kaicharla, Trinadh and Bhojgude, Sachin Suresh and Biju, Akkattu T.} } @article {42448, title = {Efficient synthesis of gamma-keto sulfones by NHC-catalyzed intermolecular stetter reaction}, journal = {Organic Letters}, volume = {14}, year = {2012}, month = {MAY}, pages = {2830{\textendash}2833}, abstract = {

The N-heterocyclic carbene-catalyzed intermolecular Stetter reaction of aldehydes with α,β-unsaturated sulfones allows the atom-economic and selective formation of γ-keto sulfones in good yields. Key to the success of this unique transition-metal-free carbon{\textendash}carbon bond-forming reaction is the right choice of the NHC precursor and base. The reaction tolerates a broad range of different aldehydes.

}, doi = {10.1021/ol301045x}, author = {Bhunia, Anup and Yetra, Santhivardhana Reddy and Bhojgude, Sachin Suresh and Biju, Akkattu T.} } @article {42447, title = {Practical and general diels-alder reaction of pentafulvenes with arynes}, journal = {Organic Letters}, volume = {14}, year = {2012}, month = {AUG}, pages = {4098{\textendash}4101}, abstract = {

A high-yielding, versatile and practical Diels{\textendash}Alder reaction of pentafulvenes with arynes under mild reaction conditions is reported. The aryne generated by the fluoride induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes efficient cycloaddition with 6-substituted and 6,6-disubstituted pentafulvenes leading to the formation of benzonorbornadiene derivatives.

}, doi = {10.1021/ol301742k}, author = {Bhojgude, Sachin Suresh and Kaicharla, Trinadh and Bhunia, Anup and Biju, Akkattu T.} } @article { ISI:000326615100015, title = {Employing arynes in transition-metal-free monoarylation of aromatic tertiary amines}, journal = {Organic Letters}, volume = {15}, number = {21}, year = {2013}, month = {NOV}, pages = {5452-5455}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The highly monoselective N-arylation of aromatic tertiary amines using a transition-metal-free approach using arynes has been developed. The reaction afforded functionalized diaryl amines in moderate to excellent yield. High levels of functional group compatibility especially with halogen containing substrates, dyes and donor-acceptor systems, and high yields of products are the notable features of the present reaction.

}, issn = {1523-7060}, doi = {10.1021/ol4029258}, author = {Bhojgude, Sachin Suresh and Kaicharla, Trinadh and Biju, Akkattu T.} } @article {42441, title = {Diels-alder reaction of tropones with arynes: synthesis of functionalized benzobicyclo[3.2.2]nonatrienones}, journal = {Journal of Organic Chemistry}, volume = {79}, year = {2014}, month = {APR}, pages = {4757{\textendash}4762}, abstract = {

A new procedure for the mild, practical, and scalable Diels{\textendash}Alder reaction of tropones with arynes is reported. Differently substituted tropones undergo selective [4 + 2] cycloaddition with arynes generated in situ by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates, allowing the formation of functionalized benzobicyclo[3.2.2]nonatrienone derivatives in moderate to good yields. In addition, the photophysical properties of the cycloadducts are presented.

}, doi = {10.1021/jo500819w}, author = {Thangaraj, Manikandan and Bhojgude, Sachin Suresh and Bisht, Rajesh H. and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article { ISI:000331163900009, title = {Efficient synthesis of 9-aryldihydrophenanthrenes by a cascade reaction involving arynes and styrenes}, journal = {Organic Letters}, volume = {16}, number = {3}, year = {2014}, month = {FEB}, pages = {676-679}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A mild, general, and transition-metal-free protocol for the synthesis of 9,10-dihydrophenanthrenes is reported. The aryne generated by the fluoride-induced,1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes an efficient cascade reaction initiated by the Diels-Alder reaction with the differently substituted styrenes leading to the formation of 9-aryl-9,10-dihydrophenanthrene derivatives in moderate to good yields.

}, issn = {1523-7060}, doi = {10.1021/ol4033094}, author = {Bhojgude, Sachin Suresh and Bhunia, Anup and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {42438, title = {Tandem [4 + 2]/[2 + 2] cycloaddition reactions involving indene or benzofurans and arynes}, journal = {Organic Letters}, volume = {16}, year = {2014}, month = {JUN}, pages = {3576{\textendash}3579}, abstract = {

The reaction of arynes with indene/benzofurans has been developed. The arynes were generated from 2-(trimethylsilyl)aryl triflates by the fluoride-induced 1,2-elimination react with indene or various benzofurans proceeding via a cascade reaction involving the Diels{\textendash}Alder reaction and a [2 + 2] cycloaddition reaction. The tandem process afforded functionalized dihydrobenzocyclobutaphenanthrenes in moderate to good yields. Moreover, the method has been utilized for the one-pot synthesis of benzo[b]fluoranthene.

}, doi = {10.1021/ol501579d}, author = {Bhojgude, Sachin Suresh and Thangaraj, Manikandan and Suresh, Eringathodi and Biju, Akkattu T.} } @article { ISI:000366878300084, title = {Three-component coupling involving arynes, aromatic tertiary amines, and aldehydes via aryl-aryl amino group migration}, journal = {Organic Letters}, volume = {17}, number = {24}, year = {2015}, month = {DEC}, pages = {6270-6273}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The transition-Metal-free multicomponent coupling of arynes, aromatic tertiary amines, and aldehydes proceeding via the aryl to aryl amino group migration has been demonstrated. This protocol allows rapid access to ortho-functionalized tertiary amines in moderate to good yields. Moreover, activated ketones can also be used as the aldehyde Component in the present reaction. The similarity of the aryl-aryl tertiary amino group migration with the Smiles rearrangement is striking.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.5b03319}, author = {Bhojgude, Sachin Suresh and Baviskar, Dnyaneshwar R. and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {42425, title = {Employing arynes in diels{\textendash}alder reactions and transition-metal-free multicomponent coupling and arylation reactions}, journal = {Accounts of Chemical Research}, volume = {49}, year = {2016}, month = {SEP}, pages = {1658-1670}, abstract = {

Conspectus

Arynes are highly reactive intermediates having several applications in organic synthesis for the construction of various ortho-disubstituted arenes. Traditionally, arynes are generated in solution from haloarenes under strongly basic conditions. However, the scopes of many of the aryne reactions are limited because of the harsh conditions used for their generation. The renaissance of interest in aryne chemistry is mainly due to the mild conditions for their generation by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates. This Account is focused on the Diels{\textendash}Alder reaction of arynes and their transition-metal-free application in multicomponent couplings as well as arylation reactions.

The Diels{\textendash}Alder reaction of arynes is a powerful tool for constructing benzo-fused carbocycles and heterocycles. In 2012, we developed an efficient, broad-scope, and scalable Diels{\textendash}Alder reaction of pentafulvenes with arynes affording benzonorbornadiene derivatives. Subsequently, we accomplished the Diels{\textendash}Alder reaction of arynes with dienes such as 1,2-benzoquinones and tropones. Moreover, we uncovered a transition-metal-free protocol for the synthesis of 9,10-dihydrophenanthrenes by the reaction of arynes with styrenes that proceeds via a Diels{\textendash}Alder/ene-reaction cascade. In addition, we demonstrated the reaction of arynes with indene/benzofurans, which proceeds via a tandem [4 + 2]/[2 + 2] sequence.

Multicomponent coupling (MCC) involving arynes mainly comprises the initial addition of a nucleophile to the aryne followed by interception of the aryl anion intermediate with an electrophile (provided the nucleophilic and electrophilic moieties do not belong to the same molecule). We have disclosed aryne MCCs initiated by N-heterocycles such as (iso)quinoline, pyridine, and aziridines. When (iso)quinoline is used as the nucleophilic trigger and N-substituted isatin as the third component, the reaction affords spirooxazino(iso)quinolines via 1,4-dipolar intermediates. Unexpectedly, using pyridine affords indolin-2-ones, where the reaction proceeds via the pyridylidene intermediate. Additionally, we developed the phosphine-triggered aryne MCCs for the synthesis of functionalized benzooxaphospholes. In another phase of our work, we studied the synthetic utility of CO2\ as a one-carbon synthon in aryne MCCs for the synthesis of phthalimides.

Engaging arynes as an aryl source is one of the transition-metal-free methods for arylation reactions. We have demonstrated the N-arylation of aromatic tertiary amines and O-arylation of aliphatic alcohols using arynes.

It is anticipated that the chemistry of arynes will continue to prosper and will lead to surprising developments for the synthesis of various 1,2-disubstituted arenes of molecular complexity and structural diversity. Future challenges in this area include the utility of arynes in enantioselective transformations and the synthesis and reactions of exotic heterocyclic arynes.

}, keywords = {2-Benzoquinones; Cycloaddition, Facile N-arylation; O-arylation; One-Pot; Aldehydes; Benzyne; Amines; Heterocycles; Acids; 1}, doi = {10.1021/acs.accounts.6b00188}, author = {Bhojgude, Sachin Suresh and Bhunia, Anup and Biju, Akkattu T.} } @article { ISI:000366864700011, title = {Employing carboxylic acids in aryne multicomponent coupling triggered by aziridines/azetidines}, journal = {Organic Chemistry Frontiers}, volume = {3}, number = {1}, year = {2016}, month = {NOV}, pages = {71-76}, publisher = {CHINESE CHEMICAL SOC}, address = {PO BOX 1-18, NANKANG, TAIPEI 115, TAIWAN}, abstract = {

The transition-metal-free aryne multicomponent coupling (MCC) involving carboxylic acids initiated by aziridines/azetidines has been reported. The use of aziridines as nucleophiles afforded N-aryl beta-amino alcohol derivatives and the application of azetidines as nucleophilic triggers furnished N-aryl gamma-amino alcohol derivatives in moderate to good yields. These reactions proceed under mild conditions and result in the formation of a new carbon-nitrogen bond and a new carbon-oxygen bond. The utility of carboxylic acids in aryne MCCs has been demonstrated, and the synthetic potential of phenols as acid surrogates in the present aryne MCCs has been realized.

}, issn = {2052-4129}, doi = {10.1039/c5qo00328h}, author = {Roy, Tony and Bhojgude, Sachin Suresh and Kaicharla, Trinadh and Thangaraj, Manikandan and Garai, Bikash and Biju, Akkattu T.} } @article { ISI:000369572000029, title = {From insertion to multicomponent coupling: temperature dependent reactions of arynes with aliphatic alcohols}, journal = {Chemical Communications}, volume = {52}, number = {8}, year = {2016}, month = {NOV}, pages = {1665-1668}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The temperature dependent selectivity switch in the reaction of arynes with aliphatic alcohols in THF has been reported. At -20 degrees C, arynes smoothly insert into the O-H bond of alcohols to form alkyl aryl ethers. Interestingly, at 60 degrees C, a highly selective multicomponent coupling occurs with the solvent THF acting as the nucleophilic trigger affording (4-(alkoxy)butoxy)arenes.

}, issn = {1359-7345}, doi = {10.1039/c5cc08307a}, author = {Thangaraj, Manikandan and Bhojgude, Sachin Suresh and Mane, Manoj V. and Biju, Akkattu T.} } @article {42430, title = {Selective synthesis of N-unsubstituted and N-arylindoles by the reaction of arynes with azirines}, journal = {Journal of Organic Chemistry}, volume = {81}, year = {2016}, month = {SEP}, pages = {8604-8611}, abstract = {

The transition-metal-free and temperature-dependent highly selective reaction of arynes with 2H-azirines allowing the synthesis of either N-unsubstituted or N-arylindoles has been developed. At 60 degrees C, arynes generated from 2-(trimethylsilyl)aryl triflates smoothly insert into 2H-azirines to form 2,3-diarylindoles with high selectivity. Interestingly, when the reaction was performed at -10 degrees C, the selectivity was switched to the formation of 1,2,3-triarylindoles in good yields.

}, doi = {10.1021/acs.joc.6b01472}, author = {Thangaraj, Manikandan and Bhojgude, Sachin Suresh and "Jain, Shailja" and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {42429, title = {Substrate-controlled selectivity switch in the three-component coupling involving arynes, aromatic tertiary amines, and CO2}, journal = {Organic Letters}, volume = {18}, year = {2016}, month = {OCT}, pages = {5424{\textendash}5427}, abstract = {

The transition-metal-free multicomponent coupling involving arynes, aromatic tertiary amines, and CO2\ is reported. The reaction exhibits switchable selectivity depending on the electronic nature of the aromatic amines used. With amines bearing electron-releasing/neutral groups as the nucleophilic trigger, the reaction afforded 2-arylamino benzoates via a nitrogen to oxygen alkyl group migration. Employing electron-deficient amines in the reaction furnished 2-aminoaryl benzoates proceeding via the aryl to aryl amino group migration resembling a Smiles rearrangement.

}, doi = {10.1021/acs.orglett.6b02845}, author = {Bhojgude, Sachin Suresh and Roy, Tony and Gonnade, Rajesh G. and Biju, Akkattu T.} }