Olefin Metathesis: A Reversible Stimulus for a Conformational Switch

Garcia, M.‐Elisa Juarez; Fröhlich, Ute; Koert, Ulrich

doi:10.1002/ejoc.200700068

Cited by 7 publications

(1 citation statement)

References 18 publications

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“…in 1963 in the same AlCl 3 mediated cycloaddition . (For ulterior [4+2] cycloadditions to buta‐1,3‐diene 3 a . For specific high pressure conditions ,.…”

Section: Introductionmentioning

confidence: 99%

Diels‐Alder Reaction of Cyclopenta‐1,3‐diene and Anthracene to bis‐Fumarates Derived from Menthol Analogues

Piątek

Chapuis

2019

ChemistrySelect

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Due to steric interactions of the overly bulky substituted 8position, the classic 8-Ph-menthol (-)-1 d is not the optimal chiral auxiliary for the asymmetric Diels-Alder reaction of its bis fumarate (-)-2 d to dienes such as cyclopenta-1,3-diene 3 b, or anthracene 3 c. This prosthetic group (-)-1 d could efficiently be replaced by an intermediate smaller analog (-)-1 e, readily prepared in a single step by cyclopropanation of isopulegol (-)-1 b. This latter auxiliary, resulting from the industrial technology developed by Takasago for menthol (-)-1 a, does not necessitate the stereoselective ketone reduction and chromatographic separation of the usual Michael adducts, derived from (+)-pulegone. This chiral auxiliary (-)-1 e, never used as an asymmetric Diels-Alder promoter, is much more selective than menthol (-)-1 a itself, under uncatalyzed conditions, and is also more stable than the polymerizable isopulegyl derived dienophiles, under Lewis acid mediated conditions. This prosthetic group thus readily allows large scale operations in both accessible enantiomeric series. Results and DiscussionThe series of known chiral auxiliaries menthol (-)-1 a, [60][61] isopulegol (-)-1 b, [62][63][64] 8-Me-menthol (-)-1 c ([α] D 20 =-38.5, c = 1.0, CHCl 3 . For several signals, our 13 C-NMR attributions based [a]

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“…in 1963 in the same AlCl 3 mediated cycloaddition . (For ulterior [4+2] cycloadditions to buta‐1,3‐diene 3 a . For specific high pressure conditions ,.…”

Section: Introductionmentioning

confidence: 99%

Diels‐Alder Reaction of Cyclopenta‐1,3‐diene and Anthracene to bis‐Fumarates Derived from Menthol Analogues

Piątek

Chapuis

2019

ChemistrySelect

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The Barton‐McCombie Reaction

2012

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Deoxygenations of alcohols, i.e., processes that replace a hydroxyl group with hydrogen at a saturated carbon, find applications in both total synthesis and the systematic modifications of natural products. They may also be employed to introduce deuterium or tritium in a site‐specific manner. Reductive methods that involve ionic or highly polarized reagents or intermediates can be limited in their applicability: for example, competing reaction pathways including cationic rearrangements and anionic eliminations may be encountered in sterically hindered systems with substrates bearing heteroatoms close to the center undergoing reduction. As evidenced by developments over the last few decades, methods that involve the generation and direct quenching via hydrogen atom abstraction of the derived, carbon‐centered radical typically show the greatest tolerance for the presence of other functional groups and for variations in both the steric acid and the electronic environment in the vicinity of the center undergoing deoxygenation. Derivatization of the hydroxyl is a prerequisite, the determinant factors for efficient formation of the deoxygenated product lies in the ability of the combination of the substrate and reagents to induce homolysis of the C‐O bond coupled with the induction of homolysis to rapidly reduce a free radical by hydrogen donation, thereby propagating an efficient chain process. A high‐yielding way to realize this sequence was first described by Barton McCombie using the free‐radical chain reaction of O ‐thioacyl derivatives of secondary alcohols with tri‐ n ‐butylstannane. This chapter provides a detailed description and comparison of the combinations of substrates and reagents that will bring about these processes and provides a summary and evaluation of alternative deoxygenation methods. Mechanistic and stereochemical issues set out the scope and limitations of these processes with respect to both the thioacylation and reduction steps and exemplify some applications to both total synthesis and the modification of natural products.

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Alkene Metathesis

2010

Comprehensive Organic Name Reactions and Reagents

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It has been found that the alkene metathesis (olefin metathesis) proceeds via insertion (or oxidative addition) followed by reductive elimination to afford the final product in the presence of only a catalytic amount of the Grubbs catalyst. Various types of ruthenium‐based metallo‐carbene complexes have been designed during the development of alkene metathesis. This general reaction can be divided into different subgroups based on the nature of alkene metathesis. A more cost‐effective method for alkene metathesis is to generate the metallo‐carbene in situ , which has a great industrial importance. Alkene metathesis is a synthetically powerful chemical transformation, enabling the synthesis of complicated molecular structures for the preparation of novel pharmaceuticals. This method has been applied to various studies for example, drug discovery, peptide synthesis, etc.

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Olefin Metathesis: A Reversible Stimulus for a Conformational Switch

Abstract: A ring-closing olefin metathesis (RCM) to an eightmembered ring is suitable to induce a conformational switch of a 2,3,6,7-tetrasubstituted cis-decalin. The double-ring flip of the decalin scaffold can be reversed by a ring-opening metathesis. The corresponding RCM to a 14-membered ring

Cited by 7 publications

References 18 publications

Diels‐Alder Reaction of Cyclopenta‐1,3‐diene and Anthracene to bis‐Fumarates Derived from Menthol Analogues

Diels‐Alder Reaction of Cyclopenta‐1,3‐diene and Anthracene to bis‐Fumarates Derived from Menthol Analogues

The Barton‐McCombie Reaction

Alkene Metathesis

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