01085nas a2200157 4500008004100000245010500041210006900146260000800215300001600223490000700239520048000246100002300726700002900749700002200778856012700800 2012 eng d00aEfficient diels-alder reaction of 1,2-benzoquinones with arynes and its utility in one-pot reactions0 aEfficient dielsalder reaction of 12benzoquinones with arynes and cDEC a6238–62410 v143 a

A new protocol for the efficient Diels–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–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.

1 aKaicharla, Trinadh1 aBhojgude, Sachin, Suresh1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/efficient-diels-alder-reaction-12-benzoquinones-arynes-and-its-utility-one-pot-reactions01048nas a2200169 4500008004100000245009600041210006900137260000800206300001600214490000700230520041600237100001700653700003300670700002900703700002200732856012400754 2012 eng d00aEfficient synthesis of gamma-keto sulfones by NHC-catalyzed intermolecular stetter reaction0 aEfficient synthesis of gammaketo sulfones by NHCcatalyzed interm cMAY a2830–28330 v143 a

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–carbon bond-forming reaction is the right choice of the NHC precursor and base. The reaction tolerates a broad range of different aldehydes.

1 aBhunia, Anup1 aYetra, Santhivardhana, Reddy1 aBhojgude, Sachin, Suresh1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/efficient-synthesis-gamma-keto-sulfones-nhc-catalyzed-intermolecular-stetter-reaction01101nas a2200169 4500008004100000022001400041245008800055210006900143260007100212300001400283490000700297520043500304100002900739700002300768700002200791856011800813 2013 eng d a1523-706000aEmploying arynes in transition-metal-free monoarylation of aromatic tertiary amines0 aEmploying arynes in transitionmetalfree monoarylation of aromati a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV a5452-54550 v153 a

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.

1 aBhojgude, Sachin, Suresh1 aKaicharla, Trinadh1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/employing-arynes-transition-metal-free-monoarylation-aromatic-tertiary-amines-001158nas a2200181 4500008004100000022001400041245010600055210006900161260007100230300001200301490000700313520043900320100002900759700001700788700002400805700002200829856012500851 2014 eng d a1523-706000aEfficient synthesis of 9-aryldihydrophenanthrenes by a cascade reaction involving arynes and styrenes0 aEfficient synthesis of 9aryldihydrophenanthrenes by a cascade re a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a676-6790 v163 a

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.

1 aBhojgude, Sachin, Suresh1 aBhunia, Anup1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/efficient-synthesis-9-aryldihydrophenanthrenes-cascade-reaction-involving-arynes-and-005204nas a2200181 4500008004100000245012200041210007100163260000800234300001400242490000700256520442000263653003504683653009704718100002904815700001704844700002204861856013904883 2016 eng d00aEmploying arynes in diels–alder reactions and transition-metal-free multicomponent coupling and arylation reactions0 aEmploying arynes in diels–alder reactions and transitionmetalfre cSEP a1658-16700 v493 a

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–Alder reaction of arynes and their transition-metal-free application in multicomponent couplings as well as arylation reactions.

The Diels–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–Alder reaction of pentafulvenes with arynes affording benzonorbornadiene derivatives. Subsequently, we accomplished the Diels–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–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.

10a2-Benzoquinones; Cycloaddition10aFacile N-arylation; O-arylation; One-Pot; Aldehydes; Benzyne; Amines; Heterocycles; Acids; 11 aBhojgude, Sachin, Suresh1 aBhunia, Anup1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/employing-arynes-diels%E2%80%93alder-reactions-and-transition-metal-free-multicomponent-coupling-and01458nas a2200205 4500008004100000022001400041245009900055210006900154260007200223300001000295490000600305520068100311100001400992700002901006700002301035700002601058700001801084700002201102856012801124 2016 eng d a2052-412900aEmploying carboxylic acids in aryne multicomponent coupling triggered by aziridines/azetidines0 aEmploying carboxylic acids in aryne multicomponent coupling trig aPO BOX 1-18, NANKANG, TAIPEI 115, TAIWANbCHINESE CHEMICAL SOCcNOV a71-760 v33 a

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.

1 aRoy, Tony1 aBhojgude, Sachin, Suresh1 aKaicharla, Trinadh1 aThangaraj, Manikandan1 aGarai, Bikash1 aBiju, Akkattu, T. uhttp://library.ncl.res.in/content/employing-carboxylic-acids-aryne-multicomponent-coupling-triggered-aziridinesazetidines-0