Jacques Dunogues

Fonctionnalisation régiosélective en position 2 de benzènes 1,3-disubstitués

Abstract Functionalisation in 2 position of benzenes 1,3-disubstituted by para -directing groups has been investigated, involving 2-trimethylsilylated intermediates when the classical methods (particularly these involving the anion in 2 position) are ineffective. Thus 2-trimethylsilyl derivatives of 1,3-dihalo- or 1,3-dimethoxybenzene have been prepared in good yields. Their conversion into the corresponding 1,2,3-trisubstituted benzenes has been conveniently performed upon acetylation, iodination or sulfonation, except in the case of the sulfonation of the 1,3-dimethoxylated compound in which the ipso effect of the silyl group is surpassed by the directing effect of the methoxy substituents. In contrast, whith the same substrate, cyanation in position 2 was successfully carried out using chlorosulfonyl isocyanate: to our knowledge this reaction is the first example of substitution of a trimethylsilyl by a cyano group in the aromatic series.

Gem-disilylcyclopropanes: préparation et utilisation en synthèse organique

Resume Une methode pratique et generale de synthese de derives gem-disilylcyclopropaniques a partir dolefines, dichlorocyclopropanation de la double liaison suivie de silylation au moyen du reactif Me3SiCl/Li/THF a 0–10°, est proposee. Lacetylation de derives bicycliques obtenue par cette voie constitue une synthese originale, bien superieure aux methodes preexistantes, des cycloalkylidene-cetones et a permis lacces a des derives dihydrofuranniques originaux.

Ène-réactivité d'allylsilanes: Fonctionnalisation et régiochimie

Abstract The hydroperoxidation of various allylsilanes by singlet oxygen has been studied. The regioselectivity of this reaction compared to those of ethyl azodicarboxylate and 4-phenyl-1,2,4-triazoline-3,5-dione, is discussed. Mechanisms are considered in the general field of the ene reaction applied to allylic organometallic Group IVB compounds. The structures of the new products (alcohols, urazoles, hydrazines) have been determined, directly or after transformations, by NMR spectroscopy.

Stereospecific Synthesis and Acylation of cis 1-Halo 2-Trimethylsilyl Ethylenes

Abstract Several routes to 1-halo 2-trimethylsilyl ethylenes have been previously proposed 1-6: from ethyn7yltrimethylilane (addition of HBr1,2), ethyltrichlorosilane (addition H by C1, followed by dehydrohalogenation and further methylation of th Si-C1 bonds)3 or by other ways 4,5, especially by reaction of (2-trimethylsilyl) vinyl lithium with dibromoethane6.

Triméthylsilylcycloalcanes: Corrélation structure-réactivité

Abstract A comparative study of the physicochemical data (IR, Raman, 1H, 13C and 29Si NMR) of four trimethylsilylcycloalkanes, ( CH 2 ) n C Hue5f8SiMe3 ( n = 2- 5), allowed a good correlation between their structure and chemical reactivity to be established. The particular chemical behaviour of trimethylsilylcyclopropane, in this series, involves an interaction between the three-membered ring and silicon, in good agreement with a (p → d)π interaction. This study provides a lot of new data for these models and exhibits exemplarily the contribution of physico-chemistry in explaining and predicting the chemical reactivity of organic substrates.

Regioselective Synthesis of 2,2-Dimethylcyclopentanone Using 2-Pyrrolidone Magnesium Salt as Electrogenerated Base.

Abstract An efficient, direct and regioselective preparation of 2,2-dimethylcyclopentanone, via its enolate precursor regioselectively obtained using the 2-pyrrolidone magnesium salt, a base electrogenerated in DME/HMPA, is reported.

COMPETITIVE ELECTROCHEMICAL SYNTHESIS OF 1-METHOXY-3,6-BIS (TRIMETHYLSILYL) CYCLOHEXA-1,4-DIENE, A KETOPROFEN PRECURSOR

Abstract The synthesis of 1-methoxy-3,6-bis (trimethylsilyl) cyclohexa-1,4-diene, a ketoprofen precursor has been achieved from anisole by an electrochemical way using an undivided cell fitted with a sacrificial aluminium anode and a stainless steel cathode, with or without solvent, under constant current density.

Polyaddition de groupes trimethylsilyles au guaiazulene

Abstract Direct silylation of guaiazulene affords a tetrasilylated derivative (yield 91%) as well as a hexasilylated compound resulting from the reductive dimerization. Both were identified by 1 H and 13 C NMR spectroscopy.