Catalyst-controlled divergence in cycloisomerisation reactions of N-propargyl-N-vinyl sulfonamides: gold-catalysed synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines

Undeela, Sridhar; Thadkapally, Srinivas; Nanubolu, Jagadeesh Babu; Singarapu, Kiran Kumar; Menon, Rajeev S.

doi:10.1039/c5cc04871k

Cited by 49 publications

(26 citation statements)

References 54 publications

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“…Investigations along this direction led to the discovery that the easily prepared 2-bromoallyl sulfones 2a , b function as allenyl sulfone surrogates in the presence of cesium carbonate ( Scheme 1 , path a). Bromoallyl sulfones 2a , b partake in a cesium carbonate-mediated formal vinylic substitution reaction with heteronucleophiles to afford valuable multifunctional building blocks [ 23 ]. For example, the reaction of 2a with 4-chlorophenol afforded the enol ether 3 in 84% yield ( Scheme 1 , path b) [ 24 ].…”

Section: Resultsmentioning

confidence: 99%

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

Thadkapally¹,

Kunjachan²,

Menon³

2016

Beilstein J. Org. Chem.

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Section: Resultsmentioning

confidence: 99%

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

Thadkapally¹,

Kunjachan²,

Menon³

2016

Beilstein J. Org. Chem.

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“…However, using a combination of (Ph 3 P)AuCl and AgSbF 6 as catalyst system, the isomerization of allene intermediate ( 219 ), followed by the 6π‐electrocyclization to yield the dihydropyridine ( 221 , Figure ). Thus, both pyrroles 220 and dihydropyridines 221 were selectively synthesized from a common enyne substrates ( 219 ) by just fine tuning the catalytic conditions …”

Section: Divergent Enyne Cycloisomerization Reactions In Scaffold DIVmentioning

confidence: 99%

Gold(I) Catalyzed Enyne Cycloisomerization – A Roadmap to Privileged Heterocyclic Scaffolds

Lee

Kumar

2018

Israel Journal of Chemistry

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Gold(I) catalyzed cycloisomerization reaction is one of the key transformations that remain underexplored to build molecular diversity and complexity. In this review, we summarize synthesis endeavors where enyne cycloisomerization chemistry was utilized to form structurally intriguing as well as biologically relevant heterocyclic scaffolds. To this goal, most of the efforts tend to exploit gold carbene type intermediates, often supporting a cyclopropane ring and transform them into new scaffolds. Various examples have been grouped together to highlight the role of presence or absence of external heteroatom nucleophiles in modulating reactive intermediates into novel molecular frameworks. The last section is devoted to the emerging role of gold(I) catalyzed cycloisomerization reactions in driving the divergent synthesis approaches wherein a common substrate can be transformed into distinct molecular scaffolds by merely varying reaction conditions or gold complexes.

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“…In two cases (R 1 =H or CO 2 Et), however, 6‐membered rings were obtained as major products. Recently, catalyst‐controlled formation of dihydropyridines as major products was observed by Menon and co‐workers in the cyclizations of N ‐propargyl‐ N ‐vinyl sulfonamides 5 (Scheme ). Somewhat surprisingly, the use of cationic gold species generated from (PPh 3 )AuCl/AgSbF 6 gave rise to dihydropyridines 7 , while Echavarren's [JohnPhosAu(MeCN)]SbF 6 induced the formation of pyrroles 6 .…”

Section: Introductionmentioning

confidence: 98%

Substrate Control in the Gold(I)‐Catalyzed Cyclization of β‐Propargylamino Acrylic Esters and Further Transformations of the Resultant Dihydropyridines

et al. 2016

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N-Protected b-propargylamino acrylic estersw ith ap ush-pull olefinic bonda ffordedg ood to high yields of dihydropyridines upont reatment with 5% tris(2-furyl)phosphine-gold(I) chloride/silver(I) tetrafluoroborate [(TFP)AuCl/AgBF 4 ]i na nhydrousb enzene.C arbamate and sulfonyl groups were employed for nitrogen protection. On am odel enyne, the p-methoxybenzenesulfonyl (MBS) group was found to be ab etter protective group than tosyl in termso fc yclization yield, and also the yield of elimination to the corresponding 2,3,4-trisubstituted pyridines.B oc-protectedd ihydropyridines underwent partiald eprotection/oxidationu nder the cyclization conditions,w hich enabled am ore straightforward, one-pot preparation of the corresponding pyridines. In another application, an appropriately substituted derivative protecteda sastablem ethoxycarbamate was subjected to catalytic hydrogenation affording the known precursor of paroxetine.T he chemoselectivity of enynec yclization (dihydropyridine vs. pyrrole) is governed, among other factors,b yC -3 substitution. Dihydropyridinesw ere obtained as sole products regardless of the catalyst/conditions when C-3 was unsubstituted.

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Catalyst-controlled divergence in cycloisomerisation reactions of N-propargyl-N-vinyl sulfonamides: gold-catalysed synthesis of 2-sulfonylmethyl pyrroles and dihydropyridines

Cited by 49 publications

References 54 publications

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

Gold(I) Catalyzed Enyne Cycloisomerization – A Roadmap to Privileged Heterocyclic Scaffolds

Substrate Control in the Gold(I)‐Catalyzed Cyclization of β‐Propargylamino Acrylic Esters and Further Transformations of the Resultant Dihydropyridines

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