Stereospecific syntheses of (E)-1,3-disubstituted dienes

Hauser, Frank M.; Tommasi, Rubén; Hewawasam, Piyasena; Rho, Young S.

doi:10.1021/jo00255a047

Cited by 18 publications

(7 citation statements)

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“…The newly formed double bond in the 3-(E)-conguration can be formed from either intermediate, with a conguration controlled by the preferred orientation of the 3,4 single bond in the intermediate. 45 Allylic strain would thus favor the 3-(E)-conguration of the diene products, in full agreement with our observations.…”

Section: Factors Controlling Regioselectivity With 2-alkyl Substitute...supporting

confidence: 91%

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

et al. 2014

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η3-Allyl palladium complexes are key intermediates in Tsuji-Trost allylic substitution reactions. It is well known that (η3-1-aryl-3-alkyl substituted allyl)Pd intermediates result in nucleophilic attack at the alkyl substituted terminus. In contrast, the chemistry of (η3-1,2,3-trisubstituted allyl)Pd intermediates is relatively unexplored. Herein we probe the regioselectivity with 1,2,3-trisubstituted allylic substrates in Tsuji-Trost allylic substitution reactions. DFT investigation of cationic (η3-1-Ph-2-B(pin)-3-alkyl-allyl)Pd(PPh3)2 intermediates predict that nucleophilic attack should occur preferentially on anti-allyls rather than the syn-isomers to generate benzylic substitution products under Curtin-Hammett conditions. Experimentally, systematic studies with 1,2,3-trisubstituted allylic substrates revealed that a Linear Free Energy Relationship (LFER) is observed when Charton steric parameters of the C-2 substituents are plotted against the log of the ratio of regioisomers. Bulkier C-2 substituents in 1,2,3-trisubstituted η3-allyl palladium intermediates provide stronger preference for nucleophilic attack at anti-oriented benzylic termini. Additionally, the geometry of 1,4-elimination products supports the presence of anti-allyl palladium intermediates.

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Section: Factors Controlling Regioselectivity With 2-alkyl Substitute...supporting

confidence: 91%

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

et al. 2014

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“…According to the Hauser [17] procedure, the acetate 12b or the diastereoisomerically pure 4-nitrobenzoate 12a was heated under reflux in dioxane in the presence of an excess of CaCO 3 and of a catalytic amount of Pd(OAc) 2 and PPh 3 (Scheme 2). Both substrates gave the same product distribution: 3,4-didehydro-g-ionone (6) was isolated in good yield (78 or 71%, resp.)…”

Section: 4-didehydro-g-ionone Isomers 6 Andmentioning

confidence: 99%

Synthesis, Olfactory Evaluation, and Determination of the Absolute Configuration of the 3,4‐Didehydroionone Stereoisomers

Serra

Fuganti

Brenna

2006

Helvetica Chimica Acta

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The synthesis of 3,4‐didehydroionone isomers 4, (+)‐6, and (−)‐6 and of 3,4‐didehydro‐7,8‐dihydroionone isomers 5, (+)‐7, and (−)‐7 was accomplished starting from commercially available racemic α‐ionone (1). Their preparation of the racemic forms 4–7 was first achieved by mean of a number of chemo‐ and regioselective reactions (Schemes 1 and 2). The enantio‐ and diastereoselective lipase‐mediated kinetic acetylation of 4‐hydroxy‐γ‐ionone (10a/10b) provided 4‐hydroxy‐γ‐ionone (+)‐10a/(±)‐10b and (+)‐4‐(acetyloxy)‐γ‐ionone ((+)12b) (Scheme 3). The latter compounds were used as starting materials to prepare the 3,4‐didehydro‐γ‐ionones (+)‐ and (−)‐6 and the 3,4‐didehydro‐7,8‐dihydro‐γ‐ionones (+)‐ and (−)‐7 in enantiomer‐enriched form. The absolute configuration of (+)‐12b was determine by chemical correlation with (+)‐(6S)‐γ‐ionone ((+)‐3) and with (−)‐(6S)‐α‐ionone ((−)‐1) therefore allowing to assign the (S)‐configuration to (+)‐6 and (+)‐7. Olfactory evaluation of the above described 3,4‐didehydroionone isomers shows a significant difference between the enantiomers and regioisomers both in fragrance feature and in detection threshold (Table).

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“…As a consequence, we decided to use an alternative method via acetylation and Pd-catalyzed elimination. This conversion gave vitispirane ( 23 ) in good yield [48]. Overall, this improved protocol gave racemic vitispirane ( 23 ) in three steps from theaspirane ( trans- 1 ) in excellent 72% overall yield.…”

Section: Resultsmentioning

confidence: 99%

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

Weidmann¹,

Schaffrath²,

Zorn³

et al. 2013

Beilstein J. Org. Chem.

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Allylic oxidations of olefins to enones allow the efficient synthesis of value-added products from simple olefinic precursors like terpenes or terpenoids. Biocatalytic variants have a large potential for industrial applications, particularly in the pharmaceutical and food industry. Herein we report efficient biocatalytic allylic oxidations of spirocyclic terpenoids by a lyophilisate of the edible fungus Pleurotus sapidus. This ''mushroom catalysis'' is operationally simple and allows the conversion of various unsaturated spirocyclic terpenoids. A number of new spirocyclic enones have thus been obtained with good regio-and chemoselectivity and chiral separation protocols for enantiomeric mixtures have been developed. The oxidations follow a radical mechanism and the regioselectivity of the reaction is mainly determined by bond-dissociation energies of the available allylic CH-bonds and steric accessibility of the oxidation site.2233

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Stereospecific syntheses of (E)-1,3-disubstituted dienes

Cited by 18 publications

References 0 publications

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

Breaking conjugation: unusual regioselectivity with 2-substituted allylic substrates in the Tsuji–Trost reaction

Synthesis, Olfactory Evaluation, and Determination of the Absolute Configuration of the 3,4‐Didehydroionone Stereoisomers

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

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