Johan F.G.A. Jansen

Enantioselective Conjugate Addition of Diethylzinc to Chalcones Catalysed by Chiral Ni(II) Aminoalcohol Complexes

Abstract Conjugate addition of diethylzinc to chalcones is catalysed by complexes prepared in situ from Ni(acac) 2 and cis-exo-N,N -dialkyl-3-aminoisoborneols or (+)- cis-endo-N,N -dimethyl-3-aminoborneol ((+)-DAB) ( 13b ). The products are obtained with enantioselectivities up to 84 %. When scalemic (−)- cis-exo-N,N -dimethyl-3-aminoisoborneol ((−)-DAIB) ( 3c ) was employed in the reaction a positive nonlinear relationship was found. Several factors which govern catalyst activity and enantioselectivity have been investigated.

Catalytic enantioselective conjugate addition of diethylzinc using NiII-DAIB complexes

Abstract The conjugate addition of diethylzinc to chalcone, catalyzed by a Ni II complex of the chiral amino-alcohol (−)-DAIB, resulted in the formation of (R)-1,3-diphenyl-penta-1-one with enantiomeric excess up to 85%.

Asymmetric 1,4-Additions to γ-Menthyloxybutenolides. (part III) Enantioselective Synthesis of (-) Eudesmin.

Abstract Based on an enantioselective Michael Addition of the aryldithiane of 3,4-dimethoxybenzaldehyde, to (5S)-methyloxy-s[5H]-furanone optically pure (−) Eudesmin was systhesized in 16% overall yield.

Asymmetric synthesis of decalines and hexahydroindanes

Abstract The intermolecular Diels Alder reactions of 5-menthyloxy-2[5H]-furanone with 1-vinylcyclohexenes, 1,2-dimethylenecyclohexane and 1-vinylcyclopentenes result in enantiomerically pure decalines and indanes with upto four(!) new asymmetric centers created in a single operation.

Asymmetric 1,4-Additions to γ-Menthyloxybutenolides. Enantiospecific Synthesis of Chiral 1,4-Butanediols.

Optically active methyl-substituted butanediols and γ-lactones were prepared from γ-menthyloxy-2[5H]-furanone.

Conjugate Additions of Grignard Reagents to α,β-Unsaturated Ketones Mediated by Diamine Zinc(II)monoalkoxides

A method for zinc-mediated 1,4-additions of Grignard reagents with alkoxides as non-tranferable ligands is described. Using a chiral TMEDA analogue upto 14% enantiomeric excess was achieved.

Asymmetric Diels Alder reactions and Michael type additions with 6(R)-3'(R)-Pantolactone- substituted-2H-Pyran-3(6H)-one.

The preparation of optically pure pyranone 2a, using d-pantolactone as a chiral auxiliairy, and its successful application in Diels Alder and Michael type additions with d.r.s of 89/11 up to 100/0 is described.

MICHAEL ADDITION OF LITHIODIPHENYLPHOSPHINE TO MENTHYLOXY-2[5H]-FURANONE - ENANTIOSELECTIVE SYNTHESIS OF S,S-CHIRAPHOS

Abstract The preparation of enatiomerically pure (2S,3S)-2,3-bis(diphenylphosphino)-butane (S,S-CHIRAPHOS) in 35% overall yield from readily available γ-menthoxybutenolide is described.

Synthesis of arylimines from N-silylamides and aryllithium compounds

Various arylimines were synthesized by the addition of N-silylated-N-alkyl-or N-aryl-amides to aryllithium compounds.

Asymmetric 1,4-Additions to γ-Menthyloxybutenolides. (part IV) Two Enantioselective Syntheses of 2-Methyl-1,4-butanediol.

Abstract Based on the asymmetric Michael addition to 5(R)- and 5(S)- menthyloxy-2[5H]-furanone two new syntheses of enantiomerically pure R- and S-2 methyl-1,4-butanediol are described.