@article {46292, title = {One-pot Au [III]-/lewis acid catalyzed cycloisomerization of nitroalkynes and [3+3]cycloaddition with donor-acceptor cyclopropanes}, journal = {Organic Letters}, volume = {21}, year = {2019}, month = {AUG}, pages = {6221-6224}, type = {Article}, abstract = {

A one-pot protocol for the synthesis of a tricyclic pseudoindoxyl scaffold from 2-nitroalkynylbenzenes, comprising of an Au(III)-catalyzed nitroalkyne cycloisomerization leading to isatogen and its [3 + 3]-cycloaddition with donor-acceptor cyclopropanes mediated by a suitable Lewis acid, has been developed.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.9b02035}, author = {Dhote, Pawan S. and Ramana, V. Chepuri} } @article {47351, title = {Gold-catalysed nitroalkyne cycloisomerization - synthetic utility}, journal = {Chemical Record}, volume = {21}, year = {2021}, month = {DEC}, type = {Article}, abstract = {

The gold-catalysed intramolecular redox cyclization of o-alkynylnitrobenzens documented by Professors Naoki Asao and Yoshinori Yamamoto is an important discovery that has opened two complementary research domains. Advancing this cyclization with other metals as well as developing new methods around the products that result from this reaction is one aspect that has seen growing interest. On the other hand, the idea of generating alpha-oxo gold carbenes via oxygen transfer to alkynes has established another important aspect in gold-catalysis. In this account, we will be dealing with the first aspect, which revolves around the internal redox cyclization of nitroalkynes (trivially called as nitroalkyne cycloisomerization), focusing mainly on the gold-complexes and the synthetic methods developed around it from our group and from other groups, and also providing the details of similar transformations documented with other metals so that the complementary reactivity/diversity of these transformations could be appreciated.

}, keywords = {alpha-Oxo Gold Carbene, Anthranil, Gold-catalysis, Internal Redox Cyclization, Isatogen}, issn = {1527-8999}, doi = {10.1002/tcr.202100111, Early Access Date = JUN 2021}, author = {Dhote, Pawan S. and Halnor, Swapnil V. and Ramana, Chepuri V.} } @article {47625, title = {Intermolecular interception of alpha-oxo gold carbenes of nitroalkyne cycloisomerization with 1, 2-benzo[d]isoxazole: synthesis of functionalized quinazoline 1-oxides}, journal = {Journal of Organic Chemistry}, volume = {86}, year = {2021}, month = {AUG }, pages = {10874-10882}, type = {Article}, abstract = {The known nitrogen-transfer reagent 1,2-benzo[d]isoxazole has been used to trap the postulated a-oxo gold carbene intermediate involved in the [Au]-catalyzed internal redox process of 2-alkynylnitrobenzenes. This process led us to develop a general convergent method for the synthesis of highly functionalized quinazoline 1-oxides.}, issn = {0022-3263}, doi = {10.1021/acs.joc.1c01221}, author = {Dhote, Pawan S. and Pund, Kishor A. and Ramana, V, Chepuri} } @article {47407, title = {Interrupting the [Au]-catalyzed nitroalkyne cycloisomerization: trapping the putative alpha-oxo gold carbene with benzo[c]isoxazole}, journal = {Organic Letters}, volume = {23}, year = {2021}, month = {APR }, pages = {2632-2637}, type = {Article}, abstract = {

The [Au]-catalyzed nitroalkyne cycloisomerization of 2-alkynylnitrobenzenes leading to anthranils has been interrupted by possible trapping of the postulated intermediate alpha-oxo gold carbene with an external nucleophile such as benzo[c]isoxazole (anthranil). At the outset, this provides a simple synthesis of highly functionalized 3-acyl-(2-formylphenyl)-2H-indazoles with the sequential C-O, C-N, and N-N bond formations. This provides indirect support for the existence of alpha-oxo gold carbenes in the [Au]-catalyzed internal redox processes of nitroalkynes.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.1c00539}, author = {Dhote, Pawan S. and Ramana, V, Chepuri} } @article {47705, title = {Total synthesis of the pseudoindoxyl class of natural products}, journal = {Organic \& Biomolecular Chemistry}, volume = {19}, year = {2021}, month = {OCT}, pages = {7970-7994}, type = {Review}, abstract = {The pseudoindoxyl sub-structural motif, amongst the large set of the indole class of alkaloids, represents a unique subset of the oxygenated indole class of the alkaloid family. A majority of this class of natural products contains complex bridged/polycyclic scaffolds with interesting biological profiles. They are thus attractive synthetic targets. Starting from 1963, twenty-eight natural products having the pseudoindoxyl scaffold have been isolated, among which the synthesis of 13 natural products has been accomplished. In this review, we highlight the completed as well as the formal total synthesis of the natural products with a spiro-pseudoindoxyl ring, with a focus on their development. The challenges and the future perspective based on the recent developments in the field will also be discussed. We strongly believe that this review will not only update but also attract the attention of researchers in dealing with the synthesis of pseudoindoxyl compounds.}, issn = {1477-0520}, doi = {10.1039/d1ob01285a}, author = {Dhote, Pawan S. and Patel, Pitambar and Vanka, Kumar and Ramana, Chepuri V.} } @article {47893, title = {Competing intra- vs intermolecular nitrene transfer in the [Au]-catalysed reaction of 2-alkynylphenylazides}, journal = {Advanced Synthesis \& Catalysis}, volume = {364}, year = {2022}, month = {MAR}, pages = {1122-1133}, type = {Article}, abstract = {

The possibility of interrupting the gold-catalysed intramolecular cyclization of 2-alkynylphenylazide derivatives, employing known nitrene transfer reagents such as anthranil and its isomer 1,2-benzisoxazole, has been attempted in search of developing simple tools for product diversification. With 1,2-benzisoxazoles, the intermolecular nitrene transfer leading to quinazoline is competitive with intramolecular azidoalkyne cyclization resulting in spiro indol-3-ylidene derivatives. However, in case of the reaction in the presence of anthranil, both intra- and intermolecular nitrene transfer processes result in the same product indol-3-ylidene.

}, keywords = {2-Benzisoxazole, Anthranil and 1, Gold catalysis, Nitrene Transfer, Quinazoline}, issn = {1615-4150}, doi = {10.1002/adsc.202101412}, author = {Dhote, Pawan S. and Ramana, V. Chepuri} } @article {48378, title = {Rediscovering Bacon{\textquoteright}s hydrazine/phenylhydrazine mediated cyclization of 2,2 {\textquoteleft}-dicarbonylbi(hetero)aryls: construction of (5-azo)-/indazolo[2,3-a]quinolines}, journal = {Organic \& Biomolecular Chemistry}, volume = {20}, year = {2022}, month = {JAN}, pages = {636-648}, type = {Article}, abstract = {

Hydrazine/phenylhydrazine-mediated reductive dicarbonyl coupling reactions have been carried out under mild conditions to provide polycyclic aromatic compounds and azo-substituted polyaromatic compounds. This method has a broad substrate scope with good functional group compatibility.

}, issn = {1477-0520}, doi = {10.1039/d1ob02207e}, author = {Dhote, Pawan S. and Ramana, V. Chepuri} }