Tandem radical cyclization to vinylogous carbonates and carbamates is developed for a new, highly stereoselective synthesis of heterocyclic angular triquinanes. The strategy is also useful to gain access to oxa- and azatriquinanes, which incorporate the spiroindoline moiety. The method is further extended to the synthesis of lactone-bearing as well as uracil-fused angular triquinanes. © 2012 American Chemical Society.

P. Niranjana

carbamic acid derivative

carbonic acid derivative

heterocyclic compound

sesquiterpene

article

chemical structure

chemistry

combinatorial chemistry

Cyclization

synthesis

Aza Compounds

Carbamates

Carbonates

Combinatorial Chemistry Techniques

Molecular Structure

Sesquiterpenes

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IIT Madras

Organic Letters

An efficient strategy was developed for the stereoselective construction of oxa- and aza-angular triquinanes employing a cascade 5 - exo - trig radical cyclization to vinylogous carbonates and carbamates. The radical precursors are readily prepared from 2-(hydroxymethyl)cyclopentenone/cyclohexenones. High diastereoselectivity is observed for the formation of angular oxa- and azatriquinanes. Diastereoselectivity drops when six-membered radical precursors are used. The strategy is found to be useful to incorporate synthetically challenging moieties such as spiroindoline, lactone-bearing, and uracil-fused angular triquinanes in a concise manner. © Georg Thieme Verlag Stuttgart - New York.

Fulltext

Synthesis (Germany)

Cascade Radical Cyclization to Vinylogous Carbonates/Carbamates for the Synthesis of Oxa- and Aza-Angular Triquinanes: Diastereoselectivity Depends on the Ring Size of Radical Precursor

A Lewis acid catalyzed tandem nucleophilic addition/oxa-Michael reaction was developed for the synthesis of cis-2,6-disubstituted tetrahydropyran (THP) derivatives in good yields with excellent diastereoselectivities. The strategy was successfully used in the construction of THP derivatives with three stereocenters in a highly stereoselective fashion. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

European Journal of Organic Chemistry

Tandem nucleophilic addition/oxa-michael reaction for the synthesis of cis-2,6-disubstituted tetrahydropyrans

A tandem SN2 alkylation/Michael addition to vinylogous carbonates based approach for the stereoselective synthesis of benzoxepines is developed. The stereoselectivity improves with an increase in the steric bulk of the substituents. The method is extended to the synthesis of benzopyranoxepines and benzoxepinopyridines with angular substituents. A tandem SN2 alkylation/Michael addition to vinylogous carbonates based approach for the stereoselective synthesis of benzoxepines is developed. The stereoselectivity improves with an increase in the steric bulk of the substituents. The method is extended to the synthesis of benzopyranoxepines and benzoxepinopyridines with angular substituents. Copyright © 2013 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Stereoselective synthesis of benzoxepines through tandem alkylation/Michael addition to vinylogous carbonates

A series of silver(i)-based coordination polymers (AgCPs) have been synthesized using three new nonchelating cis-bis-nitrile derivatives of oxa-bowls, L1-L3, as ligand components. The ligands are designed to provide conformational restrictions as well as semi-rigid directionality to the coordination vectors extended from the nitrile functionalities. The steric bulks around the oxa-bowl spacer moieties are gradually escalated to study their influence on the topologies of the ensuing AgCPs. Two silver salts i.e. AgSbF6 and AgPF6 are used to check the influence of anions on the structural architectures. Ziz-zag-sheet type 2-D AgCPs are formed with the ligands L1 and L2 possessing less steric bulk. All the metal centres are found to be tetracoordinated by nitrile-nitrogens of the same sheet giving distorted-bisphenoidal geometries. Additional short interactions of the silver(i) centres of a given sheet with the oxygen of the oxa-bowls belonging to the neighbouring stacked sheets are observed. The bulky ligand L3 behaved differently where the metal centres are tetracoordinated although only two of the ligating units are derived from the nitrile nitrogens and the remaining two are from, depending upon the counter anion, the counter anion/oxygen of oxa-bowls or two water molecules. The overall arrangements in the AgCPs of L3 are of the 2-D carpet type (for SbF6- ion) composed of interconnected chains, and 1-D ladder type (for PF6- ion) constructed from two chains. Cation-π interactions are found between the aromatic part of L3 of a given chain and the silver(i) of the adjacent chain that are interdigitated. © 2013 The Royal Society of Chemistry.

CrystEngComm

Coordination polymers via self-assembly of silver(I) and cis-bis-nitrile-oxa-bowl derivatives

A facile and general strategy is developed for the stereoselective synthesis of substituted 1,4-oxazepane derivatives through an intramolecular reductive etherification reaction. The effects of the substituents present on the oxonium ion and the position of this ion with respect to the nitrogen atom on the yield and selectivity of the reaction are also studied. A facile and general strategy is developed for the stereoselective synthesis of substituted 1,4-oxazepane derivatives through an intramolecular reductive etherification reaction. The effects of the substituents present on the oxonium ion and the position of this ion with respect to the nitrgen atom on the yield and selectivity of the reaction are also studied. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stereoselective synthesis of substituted 1,4-oxazepanes by intramolecular reductive etherification

An intramolecular, alkyne Prins type cyclization of vinylogous carbonates derived from o-alkynyl phenols is developed for the stereoselective construction of trans-2,3-disubstituted dihydrobenzofuran derivatives. Strong Lewis acids like TMSOTf catalyse this reaction efficiently. The presence of mildly electron donating groups on aryl rings increases the efficiency of the reaction. © Indian Academy of Sciences.

Journal of Chemical Sciences

Stereoselective synthesis of 2,3-disubstituted dihydrobenzofuran using alkyne Prins type cyclization to vinylogous carbonates

A one-pot, sequential 2,3-bis-functionalization of indoles bearing N-tethered vinylogous carbonates employing an intramolecular oxa-Pictet-Spengler reaction followed by electrophilic substitution is developed for the stereoselective synthesis of oxazino[4,3-a]indoles. © 2011 The Royal Society of Chemistry.

Journal	Organic Letters
ISSN	15237060
Open Access	No