Showing papers by "Samir Z. Zard published in 2009"
TL;DR: The formal synthesis of (+/-)-mersicarpine was achieved using an intermolecular radical addition-radical cyclization cascade that represents a flexible, convergent route to numerous polycyclic indole derivatives.
69 citations
TL;DR: S-Phthalimidomethyl xanthates derived from various alpha-amino acids add efficiently to a range of unactivated alkenes to give a variety of highly functionalized, protected amines.
26 citations
TL;DR: Xanthates derived from open chain or cyclic N-chloromethylanilides are capable of adding to various unactivated alkenes to give adducts which, in suitable cases, can be made to undergo ring closure onto the aromatic ring.
23 citations
TL;DR: In this paper, a radical cascade initiated by a nitrogen-centred (amidyl) radical was developed, allowing the rapid construction of galanthan frameworks, which resulted in the correction of the structure of kirkine.
19 citations
TL;DR: Various 2,3-allenols were efficiently prepared from the reaction of these TMS-substituted propargyl alcohols with TBAF.
15 citations
TL;DR: The substitution reaction of chlorocyclobutanones with dithiocarbonates (xanthates) is greatly accelerated by the addition of a mild base such as DABCO or DBU as discussed by the authors.
10 citations
TL;DR: A route to biaryl-3-carboxylate esters involving a radical 1,2-aryl migration has been developed and this strategy hinges on the radical addition of xanthate 2 to olefin 1 causing a 1, 2-aryl shift leading to alpha,beta-unsaturated ester 5, which is then converted into biaryl 10 by treatment with DBU under microwave heating.
10 citations
TL;DR: In this article, a modular route to cyclopentanols is devised based on a sequence of xanthate radical reactions followed by magnesium-mediated ketyl-olefin cyclization.
5 citations
TL;DR: In this article, a branching out with sulfones solved the problem of premature isomerization and allowed the radical addition of xanthates to a-branched allyl sulfones (see scheme; DCE=1,2-dichloroethane, TMS=trimethylsilyl).
Abstract: (Chemical Equation Presented) Branching out with sulfones: The use of allyl isopropyl sulfones solves the problem of premature isomerization and allows the radical addition of xanthates to a-branched allyl sulfones (see scheme; DCE=1,2-dichloroethane, TMS=trimethylsilyl). Highly functionalized structures can thus be rapidly assembled under mild reaction conditions by using cheap and readily available substrates and reagents. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
4 citations
TL;DR: In this paper, the authors describe the thought processes that went into solving synthetic problems, mostly related to steroids, submitted by industry and, in many cases, the evolution of the solutions into new reactions more generally useful in organic synthesis.
Abstract: This account relates the thought processes that went into solving synthetic problems, mostly related to steroids, submitted by industry and, in many cases, the evolution of the solutions into new reactions more generally useful in organic synthesis. A strong emphasis is placed on mechanistic considerations and serendipitous findings as the main basis for constructing working hypotheses from which novel reactions were derived. 1 Introduction 2 Early Steroid Problems 2.1 A Pleasant Encounter with Isocyanides 2.2 The Nitro Route to Corticosteroids 2.3 Explorations in Nitro Chemistry 3 The 16s-Methyl Problem 4 A Problem of Bile Acid Side-Chain Degradation 4.1 Planned and Unexpected Oxazoline Chemistry 4.2 New Reactions of Sulfines 4.3 An Unusual Route to Trifluoromethyl Ketones 5 From Enamides to Radical Chemistry 6 Solutions Waiting for Problems. © Georg Thieme Verlag Stuttgart.
1 citations
TL;DR: The formal synthesis of (±)-mersicarpine was achieved using an intermolecular radical addition−radical cyclization cascade as mentioned in this paper, which represents a flexible, convergent route to numerous polycyclic indole derivatives.
Abstract: The formal synthesis of (±)-mersicarpine was achieved using an intermolecular radical addition−radical cyclization cascade. This key reaction represents a flexible, convergent route to numerous polycyclic indole derivatives.
TL;DR: In this paper, arylaminomethylation of alkenes allows the rapid synthesis of open chain or polycyclic aniline derivatives, which can be made to undergo ring closure onto the aromatic ring.
Abstract: Xanthates derived from open chain or cyclic N-chloromethylanilides are capable of adding to various unactivated alkenes to give adducts which, in suitable cases, can be made to undergo ring closure onto the aromatic ring. This flexible arylaminomethylation of alkenes allows the rapid synthesis of open chain or polycyclic aniline derivatives.
TL;DR: In this article, the radical reaction of TMS-substituted xanthates with 2,2-dichlorovinyl ethyl sulfone has been shown to yield 2,3-allenols.
Abstract: The radical reaction of TMS-substituted xanthates with 2,2-dichlorovinyl ethyl sulfone afforded TMS-substituted homodichlorovinyl compounds that can be transformed into TMS-substituted propargyl alcohols. Various 2,3-allenols were efficiently prepared from the reaction of these TMS-substituted propargyl alcohols with TBAF.
TL;DR: In this paper, 2-, 3-, or 4-Pyridylmethyl radicals can be made to add to nonactivated alkenes to give a variety of otherwise inaccessible pyridine derivatives.
Abstract: SYNTHESIS 2008, No. 18, pp 2996–3008xx.xx.2008 Advanced online publication: 24.07.2008 DOI: 10.1055/s-2008-1067198; Art ID: M01708SS © Georg Thieme Verlag Stuttgart · New York Abstract: 2-, 3-, or 4-Pyridylmethyl radicals can be made to add to nonactivated alkenes to give a variety of otherwise inaccessible pyridine derivatives. Bicyclic structures can be obtained by combining the radical addition with ionic ring-closure steps.
TL;DR: A route to biaryl-3-carboxylate esters involving a radical 1,2-aryl migration has been developed in this article, which hinges on the radical addition of xanthate 2 to olefin 1 causing a 1, 2-aryl shift leading to alpha,beta-unsaturated ester 5, which is then converted into biaryl 10 by treatment with DBU under microwave heating.
Abstract: A route to biaryl-3-carboxylate esters involving a radical 1,2-aryl migration has been developed. This strategy hinges on the radical addition of xanthate 2 to olefin 1 causing a 1,2-aryl shift leading to alpha,beta-unsaturated ester 5, which is then converted into biaryl 10 by treatment with DBU under microwave heating.
TL;DR: O -Alkylhydroxylamines, often used for the preparation of bioconjugates, can be readily obtained by radical addition to suitable O -alkenylhydroxyamine derivatives as discussed by the authors.
Abstract: O -Alkylhydroxylamines, often used for the preparation of bioconjugates, can be readily obtained by radical addition to suitable O -alkenylhydroxylamine derivatives In the case of N -Boc- O -allylhydroxylamine, the addition is unexpectedly followed by elimination resulting in an overall allylation of the radical species