01234nas a2200181 4500008004100000245013800041210007000179260000800249300001400257490000700271520052900278100002300807700002300830700001700853700002400870700002200894856013600916 2015 eng d00aN-Heterocyclic carbene-catalyzed diastereoselective synthesis of β-lactone-fused cyclopentanes using homoenolate annulation reaction0 aNHeterocyclic carbenecatalyzed diastereoselective synthesis of β cMAY a9559-95620 v513 a

NHC-catalyzed annulation of enals with 2-enoylpyridines or 2-enoylpyridine N-oxides leading to the diastereoselective synthesis of β-lactone-fused cyclopentanes is reported. The reaction proceeds via the generation of homoenolate equivalent intermediates and tolerates a broad range of functional groups.

1 aMukherjee, Subrata1 aMondal, Santigopal1 aPatra, Atanu1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/n-heterocyclic-carbene-catalyzed-diastereoselective-synthesis-%CE%B2-lactone-fused-cyclopentanes01701nas a2200253 4500008004100000022001400041245011600055210006900171260007500240300001200315490000700327520074400334653002501078653002501103653002801128653002001156653002001176100003301196700002301229700002301252700002401275700002201299856012601321 2016 eng d a1433-785100aEnantioselective synthesis of spirocyclohexadienones by NHC-catalyzed formal [3+3] annulation reaction of enals0 aEnantioselective synthesis of spirocyclohexadienones by NHCcatal aPOSTFACH 101161, 69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcJAN a268-2720 v553 a

The enantioselective synthesis of pyrazolone-fused spirocyclohexadienones was demonstrated by the reaction of alpha,beta-unsaturated aldehydes with alpha-arylidene pyrazolinones under oxidative N-heterocyclic carbene (NHC) catalysis. This atom-economic and formal [3+3] annulation reaction proceeds through a vinylogous Michael addition/spiroannulation/dehydrogenation cascade to afford spirocyclic compounds with an all-carbon quaternary stereocenter in moderate to good yields and excellent ee values. Key to the success of the reaction is the cooperative NHC-catalyzed generation of chiral alpha,beta-unsaturated acyl azoliums from enals, and base-mediated tandem generation of dienolate/enolate intermediates from pyrazolinones.

10aannulation reactions10aasymmetric catalysis10aN-heterocyclic carbenes10aorganocatalysis10aspiro compounds1 aYetra, Santhivardhana, Reddy1 aMondal, Santigopal1 aMukherjee, Subrata1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/enantioselective-synthesis-spirocyclohexadienones-nhc-catalyzed-formal-33-annulation-101162nas a2200169 4500008004100000245011100041210007000152260000800222490000700230520051000237100002300747700002300770700002200793700002400815700002200839856013100861 2017 eng d00aEnantioselective synthesis of functionalized β-lactones by NHC-catalyzed aldol lactonization of ketoacids0 aEnantioselective synthesis of functionalized βlactones by NHCcat cAUG0 v823 aN-Heterocyclic carbene (NHC)-catalyzed intramolecular aldol lactonization of readily available ketoacids leading to the enantioselective synthesis of cyclopentane-fused β-lactones is presented. The reaction proceeds via the generation of NHC-bound enolate intermediates formed from the ketoacids in the presence of the peptide coupling reagent HATU and NHC generated from the chiral triazolium salt. The functionalized β-lactones are formed under mild conditions in high yields and enantioselectivities.1 aMondal, Santigopal1 aMukherjee, Subrata1 aDas, Tamal, Kanti1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/enantioselective-synthesis-functionalized-%CE%B2-lactones-nhc-catalyzed-aldol-lactonization01711nas a2200193 4500008004100000245015800041210007000199260000800269300001600277490000700293520094900300100002301249700001701272700001701289700003101306700002701337700002201364856013101386 2017 eng d00aEnantioselective synthesis of spiro γ-butyrolactones by N-heterocyclic carbene (NHC)-catalyzed formal [3+2] annulation of enals with 3-hydroxy oxindoles0 aEnantioselective synthesis of spiro γbutyrolactones by Nheterocy cFEB a2013 - 20190 v163 aThe N-heterocyclic carbene (NHC)-catalyzed enantioselective formal [3 + 2] annulation of α,β-unsaturated aldehydes with 3-hydroxy oxindoles is presented. Under oxidative conditions using the bisquinone oxidant, the reaction resulted in the synthesis of spiro γ-butyrolactones in moderate to good yields, enantioselectivity and diastereoselectivity. The reaction likely proceeds via the generation of the NHC-bound α,β-unsaturated acylazolium intermediate from enals, which was intercepted by the dioxindoles in a formal [3 + 2] pathway to form the spirocyclic compounds. However, a deeper mechanistic investigation revealed that the reaction can also proceed via the homoenolate intermediate. In this case, the dioxindole was oxidized to the corresponding isatin derivative using traces of air under basic conditions, and was intercepted with the NHC-bound homoenolate intermediate in a formal [3 + 2] pathway to afford the spiro compound.1 aMukherjee, Subrata1 aJoseph, Sumi1 aBhunia, Anup1 aGonnade, Rajesh, Ghanshyam1 aReddy, Santhi, Vardhan1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/enantioselective-synthesis-spiro-%CE%B3-butyrolactones-n-heterocyclic-carbene-nhc-catalyzed01208nas a2200193 4500008004100000245006200041210005600103260000800159300001600167490000700183520060300190100001700793700002300810700002200833700001800855700003100873700002200904856008800926 2017 eng d00aN - heterocyclic - carbene - catalyzed umpolung of imines0 aN heterocyclic carbene catalyzed umpolung of imines cMAR a2730 - 27340 v563 a

N-Heterocyclic carbene (NHC) catalysis has been widely used for the umpolung of aldehydes, and recently for the umpolung of Michael acceptors. Described herein is the umpolung of aldimines catalyzed by NHCs, and the reaction likely proceeds via aza-Breslow intermediates. The NHC-catalyzed intramolecular cyclization of aldimines bearing a Michael acceptor resulted in the formation of biologically important 2-(hetero)aryl indole 3-acetic-acid derivatives in moderate to good yields. The carbene generated from the bicyclic triazolium salt was found to be efficient for this transformation.

1 aPatra, Atanu1 aMukherjee, Subrata1 aDas, Tamal, Kanti1 aJain, Shailja1 aGonnade, Rajesh, Ghanshyam1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/n-heterocyclic-carbene-catalyzed-umpolung-imines01531nas a2200265 4500008004100000022001400041245010100055210006900156260000800225300001400233490000600247520065000253653002400903653001800927653001900945653001400964653002800978653002001006100002301026700002301049700002201072700002001094700002201114856012901136 2017 eng d a2155-543500aN-Heterocyclic carbene-catalyzed aldol-lactonization of ketoacids via dynamic kinetic resolution0 aNHeterocyclic carbenecatalyzed aldollactonization of ketoacids v cJUN a3995-39990 v73 a

N-Heteroryclic carbene (NHC)-catalyzed enantioselective aldol lactonization of acyclic ketoacids, proceeding via dynamic kinetic resolution, is presented. The carbene generated from the chiral anninoinclanol-derived triazolium salt in the presence of LiCl was the key for the success of this transformation. The reaction allowed the diastereoselective and enantioselective synthesis of cyclopentane-fused beta-lactones having three contiguous stereocenters. The reaction products are shown to undergo substrate-controlled beta-lactone opening in the presence of amines to afford succinimide derivatives with four contiguous stereocenters.

10aaldol lactonization10abeta-lactones10aDKR strategies10aketoacids10aN-heterocyclic carbenes10aorganocatalysis1 aMondal, Santigopal1 aMukherjee, Subrata1 aDas, Tamal, Kanti1 aGonnade, Rajesh1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/n-heterocyclic-carbene-catalyzed-aldol-lactonization-ketoacids-dynamic-kinetic-resolution01315nas a2200181 4500008004100000245011300041210006900154260000800223300001400231490000700245520062900252100002300881700002300904700003300927700002400960700002200984856012701006 2017 eng d00aOrganocatalytic enantioselective vinylogous michael-aidoi cascade for the synthesis of spirocyclic compounds0 aOrganocatalytic enantioselective vinylogous michaelaidoi cascade cAUG a4367-43700 v193 aEnantioselective synthesis of pyrazolone-fused spirocyclohexenols by the secondary amine-catalyzed cascade reaction of alpha,beta-unsaturated aldehydes with alpha-arylidene pyrazolinones is reported. This formal [3 + 3] organocascade reaction proceeds through a vinylogous Michael-aldol sequence to furnish the spiroheterocycles with three stereocenters including an all-carbon quaternary center in good yields and selectivities. The catalytic generation of alpha,beta-unsaturated iminium ions from enals and tandem dienolate/enolate formation from pyrazolinones are the key for the success of this spiroannulation reaction.1 aMondal, Santigopal1 aMukherjee, Subrata1 aYetra, Santhivardhana, Reddy1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/organocatalytic-enantioselective-vinylogous-michael-aidoi-cascade-synthesis-spirocyclic01313nas a2200193 4500008004100000022001400041245014700055210006900202260000800271300001400279490000700293520060200300100002300902700001600925700002000941700002000961700002200981856011601003 2018 eng d a1523-706000aEnantioselective N-heterocyclic carbene-catalyzed cascade reaction for the synthesis of pyrroloquinolines via N-H functionalization of indoles0 aEnantioselective Nheterocyclic carbenecatalyzed cascade reaction cNOV a6998-70020 v203 aFunctionalization of the indole N-H bond for enantioselective synthesis of biologically important pyrroloquinoline derivatives has been reported under oxidative N-heterocyclic carbene catalysis conditions. The interception of catalytically generated chiral alpha,beta-unsaturated acylazoliums with the indole derivatives proceeds in an aza-Michael/Michael/lactonization sequence to deliver the pyrroloquinoline derivatives in good yields, diastereoselectivities, and enantioselectivities. The simultaneous enhancement of reactivity and selectivity observed in polar aprotic solvents is noteworthy.1 aMukherjee, Subrata1 aShee, Sayan1 aPoisson, Thomas1 aBesset, Tatiana1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/enantioselective-n-heterocyclic-carbene-catalyzed-cascade-reaction-synthesis01194nas a2200181 4500008004100000022001400041245012600055210006900181260000800250300001400258490000700272520051900279100002300798700001800821700002300839700002200862856012800884 2018 eng d a1523-706000aN-Heterocyclic carbene-catalyzed enantioselective synthesis of spiro-glutarimides via alpha,beta-unsaturated acylazoliums0 aNHeterocyclic carbenecatalyzed enantioselective synthesis of spi cAUG a4499-45030 v203 a

NHC-catalyzed enantioselective [3 + 3] spiro-annulation of alpha,beta-unsaturated aldehydes with cyclic beta-ketoamides allowing the preparation of synthetically and biologically important spiro-glutarimide derivatives has been reported. The interception of the ketoamides with catalytically generated chiral alpha,beta-unsaturated acylazoliums proceeds in a Michael addition-intramolecular amidation pathway to deliver the spirocyclic products with good yield, diastereoselectivity, and enantioselectivity.

1 aMondal, Santigopal1 aGhosh, Arghya1 aMukherjee, Subrata1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/n-heterocyclic-carbene-catalyzed-enantioselective-synthesis-spiro-glutarimides-alphabeta01319nas a2200181 4500008004100000022001400041245013800055210006900193260000800262300001400270490000700284520063000291100002300921700001800944700002600962700002200988856012701010 2018 eng d a1523-706000aN-Heterocyclic carbene-catalyzed michael-michael-lactonization cascade for the enantioselective synthesis of tricyclic delta-lactones0 aNHeterocyclic carbenecatalyzed michaelmichaellactonization casca cMAY a2952-29550 v203 a

Enantioselective synthesis of tricyclic delta-lactones with three contiguous stereocenters has been demonstrated by the N-heterocyclic carbene (NHC)-catalyzed functionalization of benzylic C(sp(3))-H bonds. The NHC-catalyzed reaction of enals with dinitrotoluene derivatives under oxidative conditions proceeds via the chiral alpha,beta-unsaturated acylazoliums and produces the delta-lactones in good yields and excellent diastereoselectivity and enantioselectivity. This mild and atom-economic cascade reaction takes place in a Michael/Michael/lactonization sequence and tolerates a broad range of functional groups.

1 aMukherjee, Subrata1 aGhosh, Arghya1 aMarelli, Udaya, Kiran1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/n-heterocyclic-carbene-catalyzed-michael-michael-lactonization-cascade-enantioselective01430nas a2200145 4500008004100000245009800041210006900139260000800208300001500216490000900231520087700240100002301117700002201140856012201162 2018 eng d00aRecent advances in the organocatalytic enantioselective synthesis of functionalized -lactones0 aRecent advances in the organocatalytic enantioselective synthesi cSEP a2333-2349 0 v13 3 a

This Focus Review highlights recent developments in the organocatalytic enantioselective synthesis of -lactone derivatives. Owing to the importance of -lactones as a heterocyclic motif that is present in a variety of natural products and biologically active molecules, several catalytic methods have been developed for the synthesis of these compounds in their enantiomerically pure form. Organocatalytic methods that employ N-heterocyclic carbenes (NHCs), cinchona alkaloids, isothioureas, 4-dimethylaminopyridine (DMAP) derivatives, and phosphines have allowed the highly enantioselective synthesis of -lactones from cheap and readily available starting materials. Moreover, the inherent strain in the four-membered ring of -lactones has also been utilized in further synthetic transformations, thus making -lactones a versatile intermediate in organic synthesis.

1 aMukherjee, Subrata1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/recent-advances-organocatalytic-enantioselective-synthesis-functionalized-lactones01164nas a2200181 4500008004100000022001400041245012700055210006900182260000900251300001400260490000700274520048900281100001800770700001700788700002300805700002200828856013200850 2019 eng d a0022-326300aSynthesis of 2-Aryl naphthoquinones by the cross-dehydrogenative coupling involving an NHC-catalyzed endo-stetter reaction0 aSynthesis of 2Aryl naphthoquinones by the crossdehydrogenative c cJAN  a1103-11100 v843 a

An N-heterocyclic carbene (NHC)-catalyzed intramolecular Stetter reaction proceeding via the endo-fashion was the key step for the transition-metal-free and mild cross-dehydrogenative coupling of 2-cinnamoyl benzal-dehydes allowing for the synthesis of 2-aryl naphthoquinones. In this transformation, the carbene generated from the triazolium salt using Na2CO3 catalyzes the intramolecular Stetter reaction, which was followed by air oxidation to reinstall the C-C double bond.

1 aGhosh, Arghya1 aPatra, Atanu1 aMukherjee, Subrata1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/synthesis-2-aryl-naphthoquinones-cross-dehydrogenative-coupling-involving-nhc-catalyzed-endo01281nas a2200181 4500008004100000022001400041245011600055210006900171260000800240300001400248490000700262520061400269100001600883700002300899700002400922700002200946856013100968 2020 eng d a1523-706000aEnantioselective synthesis of tricyclic beta-lactones by NHC-catalyzed desymmetrization of cyclic 1,3-diketones0 aEnantioselective synthesis of tricyclic betalactones by NHCcatal cJUL a5407-54110 v223 a

The NHC-catalyzed desymmetrization of cyclic-1,3-diketones allowing the enantioselective construction of tricyclic beta-lactones with five contiguous stereocenters, including two quaternary stereocenters, has been developed. The mild and operationally simple addition of a-bromoenals to cyclopentane-1,3-diketone derivatives proceeds via the initial formation of chiral alpha,beta-unsaturated acylazolium intermediates and culminates in a cascade reaction, following the Michael-aldol-Iactonization pathway to deliver the beta-lactone derivatives in moderate to good yields and excellent selectivity.

1 aShee, Sayan1 aMukherjee, Subrata1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/enantioselective-synthesis-tricyclic-beta-lactones-nhc-catalyzed-desymmetrization-cyclic-1301691nas a2200277 4500008004100000022001400041245012000055210006900175260000900244300001600253490000700269520075600276653002501032653002001057653002101077653002801098653002001126100001801146700001601164700001601180700002401196700001901220700002301239700002201262856012901284 2021 eng d a1433-785100aNHC-catalyzed desymmetrization of N-aryl maleimides leading to the atroposelective synthesis of N-Aryl succinimides0 aNHCcatalyzed desymmetrization of Naryl maleimides leading to the cMAY  a12264-122680 v603 a

Although the construction of axially chiral C-C bonds leading to the atroposelective synthesis of biaryls and allied compounds are well-known, the related synthesis of compounds bearing axially chiral C-N bonds are relatively rare. Described herein is the N-heterocyclic carbene-catalyzed atroposelective synthesis of N-aryl succinimides having an axially chiral C-N bond via the desymmetrization of N-aryl maleimides. The NHC involved intermolecular Stetter-aldol cascade of dialdehydes with prochiral N-aryl maleimides followed by oxidation afforded N-aryl succinimides in good yields and ee values. Preliminary studies on rotation barrier for the C-N bond, the temperature dependence, and detailed DFT studies on mechanism are also provided.

10aasymmetric catalysis10aaxial chirality10adesymmetrization10aN-heterocyclic carbenes10aorganocatalysis1 aBarik, Soumen1 aShee, Sayan1 aDas, Soumik1 aGonnade, Rajesh, G.1 aJindal, Garima1 aMukherjee, Subrata1 aBiju, Akkattu, T. uhttps://library.ncl.res.in/content/nhc-catalyzed-desymmetrization-n-aryl-maleimides-leading-atroposelective-synthesis-n-aryl