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1.
Org Biomol Chem ; 16(42): 7891-7902, 2018 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-30306181

RESUMO

Reactions of cross-conjugated enynones,1,5-diarylpent-1-en-4-yn-3-ones, with arenes in the system TfOH-pyridine or under the action of acidic zeolite HUSY lead regioselectively to products of hydroarylation of the acetylene bond only,1,1,5-triarylpent-1,4-dien-3-ones, in yields up to 98%. These dienones add one more arene molecule to the double carbon-carbon bond in neat TfOH forming 1,1,5,5-tetraarylpent-1-en-3-ones in high yields. Cationic reaction intermediates have been studied by means of DFT calculations to elucidate plausible reaction mechanisms.

2.
J Org Chem ; 81(5): 1967-80, 2016 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-26844361

RESUMO

Conjugated 1,5-diarylpent-2-en-4-yn-1-ones add the superacid CF3SO3H to the acetylenic bond with formation of the corresponding butadienyl triflates. Under superacidic reaction conditions, these triflates are transformed into indanone or indene derivatives depending on which substituents on the aromatic ring are conjugated with the butadiene fragment. In a less acidic system (10% vol pyridine in CF3SO3H) only the formation of butadienyl triflates takes place. Cationic reaction intermediates were studied by means of NMR and DFT calculations.

3.
Chemistry ; 21(39): 13689-95, 2015 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-26239866

RESUMO

The combination of a practical and highly enantioselective organocatalytic reaction, which allows the stereoselective introduction of a benzodithiol group, with a fluorination step, gives a new and effective strategy for the stereoselective synthesis of difluorinated building blocks. The benzodithiol group is a versatile and chameleonic group that can be further functionalized before fluorination, giving customized and tailored useful synthetic strategies. As an example of the application of this facile strategy, the effective enantioselective synthesis of difluoroarundic acid is described.

4.
Chirality ; 26(10): 607-13, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24639288

RESUMO

Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN 1-type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be used to set up suitable reaction conditions in which chiral nucleophiles (enamine catalysis) or chiral electrophiles (iminium catalysis, chiral counterion catalysis) can easily be generated. Recently, we have used stabilized carbenium ions, directly available or obtained from the corresponding alcohols, in new organocatalytic stereoselective SN 1-type reactions. The commercially available carbenium ion benzodithiolylium tetrafluoroborate can be used for the straightforward organocatalytic stereoselective alkylation of aldehydes. In this account we will illustrate the application of this methodology in the total synthesis of natural products and the preparation of valuable starting materials.

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