Electroreductive hydrocoupling of activated olefins with ketones or aldehydes in the presence of trimethylchlorosilane

Electroreductive crossed hydrocoupling of ,β-unsaturated esters with aldehydes or ketones in the presence of trimethylchlorosilane afforded γ-lactones in good yields. Similarly, ,β-unsaturated nitriles gave γ-hydroxynitriles in high yields.     

Stereoselective construction of a quaternary carbon substituted with multifunctional groups: application to the concise synthesis of (+)-ethosuximide

Synthetically useful β,γ-unsaturated carbonyl compounds having a quaternary carbon at the -position were prepared with high stereoselectivity by the reaction of a dienolate anion derived from ,β-unsaturated imide having a chiral auxiliary and electrophiles (ethyl acetate and allyl iodide as the C₂ and C₃ unit, respectively). This method was applied to a short asymmetric synthesis of (+)-ethosuximide.     

Acid catalyzed ring closure reactions of electrophilic alkenes

Treatment of -acyl-,β-unsaturated ketones with sulfuric acid or dimethylformamide-hydrogen chloride or p-toluenesulfonic acid gave rise to 3-acyl-2-alkyl-4,5-dihydrofurans. Similar cyclization of -acyl-,β-unsaturated esters initially afforded 3-alkoxycarbonyl-2-alkyl-4,5-dihydrofurans which were transformed into 2-acylbutanolides on further reaction with sulfuric acid.

This acid catalyzed cyclization is strongly dependent upon the substitution pattern of the electrophilic alkenes, the acid used and reaction conditions.     

Direct conversion of β,γ-unsaturated esters into lactones induced by TMS-I

β,γ-unsaturated esters readily prepared by photodeconjugation are converted in one step into butanolides by treatment with TMS-I. The reaction has been extended to the access to -alkylidene lactones.     

Intramolecular Diels-Alder Reaction of Cyclohexa-2,4-dienones: Synthesis and Photochemical Reactions of Oxa-Homobrendanes

Synthesis of Oxa-homobrendanes having β, γ-unsaturated carbonyl chromophore and their photoreactions in singlet (¹S) and triplet (³T) excited states leading to novel bowl shaped molecules have been reported.     

Conjugate addition to chiral γ-heterosubstituted δ-lactones as pivotal synthons from L-glutamic acid. Synthesis of an optically active lignan lactone; (−)-hinokinin

Asymmetric induction in conjugate addition of new chiral γheterosubstituted-,β-unsaturated -lactones from L-glutamic acid was accomplished in high diastereoselectivity with the formation of trans(R,S)-adducts and was disclosed to serve as a versatile procedure for the asymmetric synthesis of antileukemic lignan lactones.     

Photoinduced one pot transformation of 2-phenyl-4-ethylidene-5(4H)-oxazolone and allylic alcohols to γ, δ-unsaturated N-benzoyl amides

Photolysis of 2-Phenyl-4-ethylidene-5(4H)-oxazolones in the presence of allylic alcohols resulted in a novel one-pot transformation to γ,δ-unsaturated N-benzoyl amides via decarbonylation, nucleophilic addition of allylic alcohols, photoinduced hydrogen transfer and the Claisen rearrangement.     

Copper(I)-catalyzed reaction of acylzirconocene chloride: cross-coupling and conjugate addition

For the purpose of exploring a new reaction of acylzirconocene chloride as an acyl anion donor, Cu(I)-catalyzed cross-coupling and conjugate addition reactions of acylzirconocene chloride were studied. The coupling reaction with allylic or propargylic halides efficiently proceeded to yield β,γ-unsaturated ketone or allenyl ketone derivatives, respectively. The conjugated addition reaction to ,β-enones was carried out in the presence of 2 equiv. of BF₃·OEt₂ giving 1,4-diketone compounds.     

A removable auxiliary for amidomercuration reactions: The stereoselective preparation of substituted n-acyl pyrrolidines and piperidines

Salicylamide condenses with γ,δ- or δ,-unsaturated aldehydes to give cyclic amidals which readily undergo diastereoselective mercury(II)-mediated amidocyclization. The resulting products serve as versatile intermediates for further elaboration as nitrogen heterocycles.     

The asymmetric synthesis of trans-substituted cyclopropanecarboxylic acid derivatives

The asymmetric synthesis of trans-substituted cyclopropanecarboxylic acid derivatives is achieved via stereoselective nucleophilic methylene transfer to E-,β-unsaturated acyl ligands bound to the iron chiral auxiliary [(η⁵-C₅H₅)Fe(CO)(PPh₃)].     

Double bond shifts induced by reaction of hex-5-en-2-one with triosmium clusters

Carbon---hydrogen bond cleavage at the terminal 6-position occurs when hex-5-en-2-one (CH₂=CHCH₂CH₂COMe) oxidatively adds to [Os₃(CO)₁₀(MeCN)₂] to give [Os₃H(μ-CH=CHCH₂CH₂COMe)(CO)₁₀], which is completely analogous to the simple vinyl complex [Os₃H(μ-CH=CH₂)(CO)₁₀]. A minor product from the reaction is [Os₃(CH₃CH=CHCH₂COMe)(CO)₁₀], an isomer in which double-bond migration has occurred to give the βγ-unsaturated ketone; stabilisation occurs through chelation and ketone coordination. [Os₃H₂(CO)₁₀] reacts with CH₂=CHCH₂CH₂COMe in refluxing cyclohexane to give a third isomer, [Os₃H(CH₃CH₂C=CHCOMe)(CO)₁₀], in which further double bond migration has occurred to give the β-unsaturated ketone. Metallation at the β-site gives an Os---C bond as part of a 5-membered chelate ring. Thermolysis of each of the three isomeric decarbonyl species in refluxing cyclohexane or heptane leads to the elimination of an Os(CO)₄ group to give the dinuclear compound [Os₂H(EtC=CHCOMe)(CO)₆] in varying yield. Pathways from γδ to the βγ and finally the β unsaturated ketones may be mapped out.     

The asymmetric synthesis of cis-substituted cyclopropanecarboxylic acid derivatives

The asymmetric synthesis of cis-substituted cyclopropanecarboxylic acid derivatives is achieved via stereoselective electrophilic methylene transfer to Z-,β-unsaturated acyl ligands bound to the iron chiral auxiliary [(η⁵-C₅H₅Fe(CO)(PPh₃)].     

The octant rule: XXIII. antioctant effects in γ,δ -unsaturated ketones.

The and -benzyl derivatives (1 and 2, respectively) of (+)-camphor have been synthesized and are found to exert a strong influence on the circular dichroism n→π^* Cotton effects: 1: Δε³⁰¹_max -0.36 (n- heptane) and 2: Δε³⁰²_max +3.22, relative to camphor: Δε³⁰⁴_max +1.8 (n-heptane). Evidence for electric dipole transition moment coupling in these γ, δ -unsaturated systems is found in the n→π^* UV: 1: ε²⁹¹_max 84 (n-heptane) and 2: ε²⁸⁵_max 303, relative to camphor: ε²⁹⁰_max 25.     

The syntheses of siccanochromene-A and the related triprenyl-phenols

Siccanochromene-A (II), episiccanochromene-B (XI) were synthesized from orcinol and a corresponding ,β-unsaturated aldehyde. Dihydro-γ-ionone which was used for the synthesis of presiccanochromene-A (XVII) was prepared photochemically from dihydro--ionone.     

The effect of a positive charge on a π → π-transition

The position of the maximum for the π → π^*-transition of a bicyclic ketone containing a quaternary nitrogen atom at 3·1 Å from an :β-unsaturated ketone system is shown to depend largely upon electrostatic (repulsion) destabilization in both ground and excited states, the latter being affected more strongly.     

An efficient synthesis of N-benzyl-3-sulfonyl glutarimides. Formal synthesis of the aromatase inhibitor AG-1

A formal [3+3] cycloaddition strategy to substituted glutarimides was studied. N-Benzyl -sulfonylacetamides and various ,β-unsaturated esters were used as starting materials.     

Preparation and reactivity of lithium 1,4-dioxenyl cuprates

Reactions of lower and higher order cuprates generated from lithiated 1,4-dioxene and copper (I) species, with epoxides and ,β-unsaturated ketones are desribed.     

Correction: Iridium-catalyzed enantioselective olefinic C(sp2)–H allylic alkylation

The first iridium-catalyzed enantioselective olefinic C(sp²)–H allylic alkylation is developed in cooperation with Lewis base catalysis. This reaction, catalyzed by cinchonidine and an in situ generated cyclometalated Ir(i)/phosphoramidite complex, makes use of the latent enolate character of an α,β-unsaturated carbonyl compound, namely coumalate ester, to introduce an allyl group at its α-position in a branched-selective manner in moderate to good yield with good to excellent enantioselectivities (up to 98 : 2 er).

The first iridium-catalyzed enantioselective allylic alkylation of an olefinic C(sp²)–H bond – that of an α,β-unsaturated carbonyl compound, is developed in cooperation with Lewis base catalysis.     

C---H bond activation by rhodium(I) and the mechanism of the olefin isomerization: new synthesis of β,γ-unsaturated ketones via η- or η-alkylallylrhodium(III) complexes by reductive elimination

Acylrhodium(III)-η³-1-ethylallyl complex (7) was prepared by the reaction of 8-quinolinecarboxaldehyde (3) and 1,4-pentadienerhodium(I) chloride (2) by C---H bond activation, followed by hydrometallation, and double bond migration. Higher concentrations of pyridine as coordinating ligand transforms η³-1-ethylallylrhodium(III) complexes (8a,8b) into η¹-pent-2-enylrhodium(III) complex (11a). Acylrhodium(III)-η³-syn,anti-1,3-dimethylallyl complex (14) was also prepared from 1,3-pentadienerhodium(I) chloride (16) and 3. The reductive elimination of acylrhodium(III)-η¹- and -η³-1-alkylallyl complexes by trimethylphosphite gives various β,γ-unsaturated ketones.     

Convenient synthesis of (1H)-isoindoles and cyclopenta[c]pyrrole skeletons

Diels-Alder reactions of various , β-unsaturated cycloalkenones with 4-methyl-5-ethoxy-oxazole in the presence of ZnBr₂ provide hydro-(1H)-isoindoles and hydrocyclopenta[c]pyrrole.