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Subrata Ghosh

Bio: Subrata Ghosh is an academic researcher from Indian Association for the Cultivation of Science. The author has contributed to research in topics: Ring-closing metathesis & Metathesis. The author has an hindex of 21, co-authored 138 publications receiving 1322 citations. Previous affiliations of Subrata Ghosh include Leipzig University & Case Western Reserve University.


Papers
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Journal ArticleDOI
TL;DR: Ring-closing metathesis has been applied to a series of glucose derivatives to produce cyclopentene derivatives 5a and 5b, cyclohexene derivatives 8 and 9, cycleheptene 12, and cyclooctene 14, and a range of fused oxepine derivatives 29a-c and one oxo-cyclononene 31.
Abstract: Ring-closing metathesis has been applied to a series of glucose derivatives to produce cyclopentene derivatives 5a and 5b, cyclohexene derivatives 8 and 9, cycloheptene 12, and cyclooctene 14. Spirocyclic dihydrofurans 19, 26a, and 26b, along with dihydropyran 22, were also produced. A range of fused oxepine derivatives 29a-c and one oxo-cyclononene 31 were also prepared. Cyclopentene 5b was subjected to a sequence of hydrogenation, NBS bromination, and treatment with powdered zinc to furnish the ring-expanded product 35. No such ring expansion occurred when the cyclohexaannulated compound 8 was treated with NBS followed by powdered zinc, leading to aldehyde 39. The spiro dihydrofuran derivative 19 was converted to the aldehyde 42 via the same reaction sequence used to fragment cyclopentene derivative 5b.

61 citations

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TL;DR: Domino metathesis involving ROM-RCM of appropriately constructed norbornene derivatives having multiple alkene chains leads to direct access of highly functionalized bridged tricyclic compounds.

51 citations

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TL;DR: A stereocontrolled approach for the construction of ABC ring systems of micrandilactone A and lancifodilact one G has been developed and a remarkable regioselectivity during hydroboration of the cycloheptene derivative 17 was observed during its transformation to the cycleheptanone 20.
Abstract: A stereocontrolled approach for the construction of ABC ring systems of micrandilactone A and lancifodilactone G has been developed. The synthesis involves construction of an enantiopure functional...

47 citations

Journal ArticleDOI
TL;DR: Les methoxydihydro benzofurannes ou methoxychromannes sont produits par cyclisation des derives demethyles par l'ethanethiolate de sodium dans le DMF.
Abstract: Les groupes methoxy en ortho des substituants β-hydroxyethyl ou γ-hydroxypropyl dans les derives de polymethoxybenzenes sont regioselectivement demethyles par l'ethanethiolate de sodium dans le DMF. Des methoxydihydro benzofurannes ou methoxychromannes sont produits par cyclisation des derives demethyles

42 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview of the development of catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups.
Abstract: The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

1,614 citations

Journal ArticleDOI
TL;DR: Photochemical Electron-Transfer Reactions with a Catalytic Sensitizer 1068 6.1.1 Photochemical Extrusion of Small Molecules 1067 6.2.2 Photochemical Rearrangings 1061 4.4.3.
Abstract: 2.3. [4 + 4] Cycloadditions 1058 2.4. Photocycloadditions of Aromatic Compounds 1058 2.4.1. Benzene Derivatives 1058 2.4.2. Condensed Aromatic Compounds 1060 3. Photochemical Rearrangements 1061 4. Cyclizations 1064 4.1. Pericyclizations 1064 4.2. Norrish−Yang Reaction 1066 5. Photochemical Extrusion of Small Molecules 1067 6. Photochemical Electron Transfer 1068 6.1. Photochemical Electron-Transfer Reactions with a Catalytic Sensitizer 1068

1,046 citations

Journal ArticleDOI
TL;DR: New, effective, and more environmentallybenignmethodologiesfortheformation of(cyclo)alkyl-aryl bonds, which require a reduced number of synthetic operations, have emerged as valuable alternatives to the conventional cross-coupling reactions.
Abstract: Transition metal-catalyzed cross-coupling reactions of alkyl metals and aryl halides or pseudohalides have emerged as a powerful methodology for the formation of Csp3-Csp2 bonds over the past decades.1 However, significant attention has also been focused on Pdand Ni-catalyzed Csp3-Csp2 bond-forming reactions that involve aryl metals and haloalkyl compounds lacking -hydrogen atoms as cross-coupling partners.2 In contrast, until a few years ago, few examples were reported in the literature concerning transition metalcatalyzed reactions of aryl metals with functionalized alkyl halides including R-halocarbonyl compounds and R-bromosulfones bearing -hydrogen atoms,3 and a single example of Pd-catalyzed cross-coupling reaction of aryl metals and unfunctionalized alkyl halides bearing -hydrogen atoms had been described.4 Only in recent years, successful procedures for the Pd-,5 Ni-,6 Rh-,7 Fe-,8 V-,9 Co-,10 and Cu-catalyzed11 cross-coupling reactions of aryl metals and unfunctionalized alkyl halides bearing -hydrogen atoms have been developed.12 Nevertheless, new, effective, and more environmentallybenignmethodologiesfortheformationof(cyclo)alkyl-aryl bonds, which require a reduced number of synthetic operations, have emerged as valuable alternatives to the conventional cross-coupling reactions. These methodologies (Scheme 1) are based on transition metal-catalyzed simple or 2-fold C-H bond functionalization according to the following approaches: (a) highly regioselective Pd-catalyzed direct arylation reactions of unactivated sp3-hybridized C-H bonds with aryl halides (eq a, Scheme 1);13 (b) Pd-catalyzed direct alkylation reactions of aryl C-H bonds with alkyl metals (eq b, Scheme 1);14 Au-15 or Pdcatalyzed16 direct alkylation reactions of aryl C-H bonds with alkyl halides or pseudohalides (eq c, Scheme 1); (d) Pd-catalyzed arylations of unactivated sp3-hybridized C-H bonds with aryl metals (eq d, Scheme 1);14c (e) Pd-, Ru-, or Cu-catalyzed cross-coupling reactions of sp3-hybridized C-H bonds with arylboronic acids using air as oxidant (eq d, Scheme 1);17 and (f) cross-dehydrogenative coupling of alkyl and aryl C-H bonds (eq e, Scheme 1).18 Finally, great attention, particularly in the past decade, has also been focused on the design, development, and application of transition metal-catalyzed coupling reactions of aryl halides and pseudohalides with a wide variety of substrates containing activated sp3-hybridized C-H bonds (eq f, Scheme 1). A mini-review on this topic was published by Scolastico and Poli in 1999,19 and three excellent reviews that concern the results obtained in this rapidly growing area of extensive research by the groups of Miura, Natsume, Hartwig, and Buchwald up to the end of 2002 were published by Miura,20 Hartwig,21 and Lloyd-Jones22 a few years later. However, the reviews by Miura20 and Hartwig21 were limited in that they fundamentally emphasized the author’s own work and * To whom correspondence should be addressed. E-mail: rossi@dcci.unipi.it. Chem. Rev. 2010, 110, 1082–1146 1082

752 citations

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TL;DR: This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds for complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis.
Abstract: The use of photochemical transformations is a powerful strategy that allows for the formation of a high degree of molecular complexity from relatively simple building blocks in a single step. A central feature of all light-promoted transformations is the involvement of electronically excited states, generated upon absorption of photons. This produces transient reactive intermediates and significantly alters the reactivity of a chemical compound. The input of energy provided by light thus offers a means to produce strained and unique target compounds that cannot be assembled using thermal protocols. This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds. Synthetic designs based on photochemical transformations have the potential to afford complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis.

692 citations