Lya Wartski

High degree of exo selectivity in imino Diels-Alder reactions catalyzed by tert-butyldimethylsilyltriflate

Abstract Diels-Alder reactions of silyloxydiene 1 derived from 1-acetylcyclohexene with imines 2b and 2c occur with high exo selectivity depending upon experimental conditions: exo cycloadducts 3b–c are exclusively formed under kinetic control using tert-butyldimethylsilytriflate as catalyst. In the presence of AlCl3, under thermodynamic control, high endo selectivity is only observed with 2b.

Stereoselective synthesis of cis or trans N-phenyl 2-phenyl decahydroquinolin-4 ones by catalyzed hetero-Diels-Alder reaction.

Cis or trans N-phenyl 2-phenyl decahydroquinolin-4 ones can be synthesized highly selectively.

Enantioselective synthesis of unsubstituted and 3-substituted-4-aroyl-δ-lactones. Easy way to enantiopure bicyclic lactone systems

Abstract Michael addition of lithiated chiral aminonitriles 1a,b to α,β-unsaturated lactone 2 afforded (4R)-aroyl-δ-lactones 8a,b with a ee value ≥ 99%. Michael addition / subsequent α alkylation process gave the corresponding (3S)-substituted-(4R)-aroyl-δ-lactones 9–10a, 9b with a ee value of 66 up to 87% and 11–12a with high enantiomeric purity the ee being ≥ 99%. The absolute configuration of the Michael adduct 7a was established by X-ray analysis and as a result that of all the other compounds was assigned. Lewis acid catalyzed cyclization of (3S,4R)-12a provided the enantiomerically pure hydroxy bicyclic lactone (4aR,5S,8aS)-13a.

Aminonitrile and cyanohydrin ethers as benzoyl anion equivalents in conjugate additions to substituted α cyclenones : comparative synthetic potentialities

Abstract Lithiated aminonitrile 1a and cyanohydrin ether 2a are good nucleophilic benzoyl equivalents in conjugate addition to α cyclenones. 1a is more sensitive to β substitution of the cyclenone than 2a , as in THF it does not react with 3-methyl substituted cyclohexenones 6a , b . From 2-methyl and 2-fluorocyclenones and 1a or 2a , cis 2-subsyituted 3-benzoylcyclanones are stereoselectively obtained, provided that mild unmasking conditions were used. The intermediate enolates trapping, leading to trans 2-substituted 3-benzoylcyclanones, is discussed, according to the nucleophilic reagent and the alkylating agent nature. A comparison with silyl ether cyanohydrin 2b shows the broader synthetic usefulness of 1a and 2a .

Influence of the Lewis acid on the nucleophilic addition to β,β-disubstituted α-enones.

Lewis acids as BF3.Et2O, Ti(OiPr)4, ZnCl2 allow the Michael addition of lithiated aminonitrile 1 to β,β-disubstituted α-enones leading thus after carbonyl unmasking to the corresponding diketones.

Addition conjuguee d'aminonitriles, equivalents de benzoyle, aux cyclenones. Quelques exemples de syntheses stereoselectives de cyclanones 2,3-disubstituees cis.

Abstract Conjugate addition of benzoyl anion equivalents to unsubstituted and 2-substituted cyclenones is proved in some cases to be highly stereoselective. Cis 2-methyl 3-benzoyl cyclanones are obtained with excellent yields.

Stereoselective synthesis of cis ring fused endo or exo octahydropyrindin-4 ones by imino-Diels-Alder reaction

The Diels-Alder reaction of trimethylsilylenolether of 1-acetylcyclopentene 1b with benzylideneaniline 2, catalyzed by AlCl3, occurred with high exo or endo selectivity, depending upon kinetic or thermodynamic control. MeOH/Et3N treatment of the intermediate cycloadducts 3 and 4 gave stereospecifically the cis ring fused exo or endo octahydropyrindin-4 onex 5 and 6 while α,β unsaturated ketones 8 or 9 were formed after acidic treatment. Basic isomerization of 6 afforded the corresponding trans ring fused endo ketone 7.

Effect of aggregation of nitrile anions on the 1,2 versus 1,4 regioselectivity towards benzylideneacetone

Abstract A direct evidence of the influence of aggregation state of lithiated phenylacetonitrile 1 on the 1,2 versus 1,4 regioselectivity towards benzylideneacetone 2 was established. Progressive addition of hexane to THF solutions raised the aggregates proportion of 1 as evidenced by IR νCN band and led to an increase of 1,4 adduct. Monomers afforded 1,2 addition in pure THF.