V. Agati

Bio: V. Agati is an academic researcher from Centre national de la recherche scientifique. The author has contributed to research in topics: Cycloaddition & Allylic rearrangement. The author has an hindex of 2, co-authored 6 publications receiving 37 citations.

Allenyl allylic ethers: synthesis and thermal rearrangements

Abstract: Application of the sequence halogenation/dehydrohalogenation/isomerization to alkenes 1a-g affords allenyl allylic ethers 5a-g. Thermal isomerizations of 5a,d,e proceed by Claisen rearrangement, while 5b,c,f,g are transformed by alternate modes of [2+2]cycloaddition involving biradical intermediates of type 19 to polycyclic structures; the variations in these thermal isomerizations are mainly a function of ring size

Diels-Alder intramolecular cycloaddition of vinylallenyl cycloalken-3-yl ethers

Abstract: Cohalogenation of cycloalkenes 1 by N-bromosuccinimide (NBS) in 4-methylpent-4-en-2-yn-1-ol affords β-bromopent-4-en-2-ynyl ethers 2 which undergo facile base-promoted consecutive dehydrohalogenation-isomerization-intramolecular Diels–Alder cycloaddition leading to tricyclic conjugated enol ethers 6.

Synthesis and reactivity of allenylvinyl cycloalk-2-enyl ethers

Abstract: Cohalogenation of alkenes 6 by N-bromosuccinimide (NBS) in 3-methylpent-2-en-4-yn-1-ol provides β-bromo-3-methylpent-2-en-4-ynyl ether 7 precursors of 3-(penta-1,3,4-trienyloxy)cycloalkenes 9 which react chemo-and regio-selectively with NBS in methanol to give bromovinyl acetals10.

Allenyl Allylic Ethers: Synthesis and Thermal Rearrangements.

Abstract: Application of the sequence halogenation/dehydrohalogenation/isomerization to alkenes 1a-g affords allenyl allylic ethers 5a-g. Thermal isomerizations of 5a,d,e proceed by Claisen rearrangement, while 5b,c,f,g are transformed by alternate modes of [2+2]cycloaddition involving biradical intermediates of type 19 to polycyclic structures; the variations in these thermal isomerizations are mainly a function of ring size

Diels-Alder Intramolecular Cycloaddition of Vinylallenyl Cycloalken-3- yl Ethers.

Abstract: Cohalogenation of cycloalkenes 1 by N-bromosuccinimide (NBS) in 4-methylpent-4-en-2-yn-1-ol affords β-bromopent-4-en-2-ynyl ethers 2 which undergo facile base-promoted consecutive dehydrohalogenation-isomerization-intramolecular Diels–Alder cycloaddition leading to tricyclic conjugated enol ethers 6.

Design and Synthesis of Highly Potent HIV-1 Protease Inhibitors Containing Tricyclic Fused Ring Systems as Novel P2 Ligands: Structure-Activity Studies, Biological and X-ray Structural Analysis.

Abstract: The design, synthesis, and biological evaluation of a new class of HIV-1 protease inhibitors containing stereochemically defined fused tricyclic polyethers as the P2 ligands and a variety of sulfonamide derivatives as the P2' ligands are described. A number of ring sizes and various substituent effects were investigated to enhance the ligand-backbone interactions in the protease active site. Inhibitors 5c and 5d containing this unprecedented fused 6-5-5 ring system as the P2 ligand, an aminobenzothiazole as the P2' ligand, and a difluorophenylmethyl as the P1 ligand exhibited exceptional enzyme inhibitory potency and maintained excellent antiviral activity against a panel of highly multidrug-resistant HIV-1 variants. The umbrella-like P2 ligand for these inhibitors has been synthesized efficiently in an optically active form using a Pauson-Khand cyclization reaction as the key step. The racemic alcohols were resolved efficiently using a lipase catalyzed enzymatic resolution. Two high resolution X-ray structures of inhibitor-bound HIV-1 protease revealed extensive interactions with the backbone atoms of HIV-1 protease and provided molecular insight into the binding properties of these new inhibitors.

Reductive free-radical alkylations and cyclisations mediated by 1-alkylcyclohexa-2,5-diene-1-carboxylic acids

Abstract: A range of 1-alkylcyclohexa-2,5-diene-1-carboxylic acids were prepared by Birch reduction–alkylation of benzoic acid and their efficiency as mediators of alkyl radical chain addition and cyclisation processes was investigated. Reductive alkylations were respectably successful, even with only one or two equivalents of alkene, for secondary, tertiary and benzylic radicals. Reaction of 1-[2-(cyclohex-2-enyloxy)ethyl]cyclohexa-2,5-diene-1-carboxylic acid yielded the product of exo-trig-cyclisation, i.e. 7-oxabicyclo[4.3.0]nonane, in a yield comparable to that obtained from the tributyltin hydride induced cyclisation of 3-(2′-iodoethoxy)cyclohexene. This, together with the isolation of both exo- and endo-cyclisation products from 1-[2-(6,6-dimethylbicyclo[3.1.1]hept-2-en-2-ylmethoxy)ethyl]cyclohexa-2,5-diene-1-carboxylic acid established that ring closures could also be satisfactorily mediated with these reagents. Preparations were completely free of metal contaminants and direct reduction of the alkyl radicals, prior to addition or cyclisation, was completely absent. However, the desired products were accompanied by alkylbenzenes, together with by-products from the initiator decompositions, and this complicated work-up. Failure to obtain 1-[2-(prop-2-yn-1-yloxy)cyclohexyl]cyclohexa-2,5-diene-1-carboxylic acid in Birch reductive alkylations with trans-1-iodo-2-(prop-2-yn-1-yloxy)cyclohexane (and the corresponding bromide) indicated a limitation on precursor synthesis. The Birch reduction–alkylation was not of universal applicability and was suppressed for alkyl halides having β-substituents.

The chemistry of bisallenes

Abstract: This review describes the preparation, structural properties and the use of bisallenes in organic synthesis for the first time. All classes of compounds containing at least two allene moieties are considered, starting from simple conjugated bisallenes and ending with allenes in which the two cumulenic units are connected by complex polycyclic ring systems, heteroatoms and/or heteroatom-containing tethers. Preparatively the bisallenes are especially useful in isomerization and cycloaddition reactions of all kinds leading to the respective target molecules with high atom economy and often in high yield. Bisallenes are hence substrates for generating molecular complexity in a small number of steps (high step economy).