Laurent De Buyck

The essential oil of Nepeta nuda. Identification of a new nepetalactone diastereoisomer

Abstract The essential oils of nine specimens of N. nuda were prepared by steam distillation, and analysed by GC and GC/MS. Thirty-seven substances were identified, accounting for 91.6–99% of the oils. They all contained varying amounts of 1,8-cineole, a mixture of nepetalactones and germacrene-D as chief components. In seven samples the new 4aβ,7α,7aα-nepetalactone was found. It was isolated, and identified by 1 H and 13 C NMR.

The volatiles of Calamintha nepeta subsp. Glandulosa

Abstract The volatiles of C. nepeta subsp. glandulosa were studied by analysis of the essential oil and of the headspace (after concentration on Tenax GC). Amongst the 27 compounds identified in the essential oil, up to 92 % consisted of piperitone oxide and piperitenone oxide, the relative concentrations of which depended on the maturity of the plants. The weak fragrance of the intact plant originated mainly from limonene and piperitone oxide. During the preparation of the essential oil, trans -sabinene hydrate and piperitone oxide isomerized in part into terpinen-4-ol and 4-hydroxypiperitone, respectively.

Reactivity of α-chloro-aldimines☆

Abstract A series of secondary N-1-(2-chloroalkylidene)amines has been prepared by condensation of disubstituted acetaldehydes with primary amines followed by chlorination with N-chlorosuccinimide in carbontetrachloride. A study of the reactivity of these N-homologues of α-chloroaldehydes is described. Treatment of the title compounds with sodium methoxide in methanol gave high yields of α,β-unsaturated aldimines. However, N-1-(2-chloro-2-methylpropylidene)amines afforded a mixture of elimination and rearrangement products, which proceeded via an aziridine intermediate. On the other hand, α-phenyl-substituted α-chloro aldimines on treatment with methoxide in methanol underwent α-substitution, consistent with an S N 1 mechanism. Powerful nucleophiles such as sodium thiophenolate in methanol and sodium azide in acetone caused α-substitution. Reaction of α-chloro aldimines with Grignard reagents produced coupling of two aldimine units or α-alkylation. Finally the reactivity of α-chloro aldimines was compared with the reactivity of the corresponding oxygen-analogues, i.e. α-chloro aldehydes.

The influence of benzylic protection and allylic substituents on the CuCl-TMEDA catalyzed rearrangement of N-allyl-N-benzyl-2,2-dihaloamides to gamma-lactams. Application to the stereoselective synthesis of pilolactam.

Abstract A number of N-benzylic protecting groups and allylic substituents have been investigated for the rearrangement, promoted by CuCl-TMEDA, of N-allyl-2,2-dihaloamides to 3,4-disubstituted γ-lactams. An appreciable chiral induction was observed at the C-4 site when α-phenylethylamine was used as a chiral protecting group, while an unexpected Diels-Alder reaction occurred when using a 2-furyl-methyl protection. This rearrangement has been applied to the synthesis of pilolactam, a drug with muscarinic activity.

Synthesis of α-cyanoenamines : Isolation and characterization of both tautomeric isomers: α-cyanoenamines and imidoylcyanides

Abstract α-Cyanoenamines have been prepared in high yield by the reaction of α-chloroaldimines with potassium cyanide in methanol. On gas chromatographic analysis, the α-cyanoenamines were partially isomerized to the tautomeric imidoylcyanides. Both isomers have been isolated and spectroscopically characterized.

Synthesis of 5-methoxylated 3-pyrrolin-2-ones via the rearrangement of chlorinated pyrrolidin-2-ones

The reaction of N-substituted 4-methyl-2-pyrrolidinones or 4-diethoxyphosphoryl analogues, carrying at least two chlorine atoms between the C(3) and C(6) carbons, with alkaline methoxide in methanol afforded the corresponding 5-methoxylated 3-pyrrolin-2-ones, useful adducts for the preparation of agrochemicals or medicinal compounds.

The Essential Oils of Calamintha nepeta subsp. glandulosa and Ziziphora clinopodioides from Turkey

ABSTRACT The essential oils of two wild growing plants used as herbal tea and mintlike spice in Turkey, Calamintha nepeta (L.) Savi subsp. glandulosa (Req.) P. W. Ball and Ziziphora clinopodioides Lam. were analyzed by GC and GC/MS. Twenty-three components were identified in both oils with pulegone (42.0%) and piperitenone (40.4%) being the major components in the Calamintha oil, and pulegone (60.2%), menthone (13.6%) and menthol (10.9%) being the major components in the Ziziphora oil were the main components.

Acid catalyzed ring closure reactions of electrophilic alkenes

Abstract Treatment of α-acyl-α,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 α-acyl-α,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.

Friedel-crafts reaction of α-chloroaldimines : possible intermediacy of α-imidoylcarbenium ions

Abstract α-Chloroaldimines are arylated at the α-position under Friedel-Crafts conditions via intermediacy of α-imidoylcarbenium ions.

Improved Synthesis of 1-Aryl-2, 2-Dichloro-1-Alkanones

Abstract Recently1 we described a convenient synthesis of 1-aryl-2, 2-dichloro-1-alkanones 1 by a reaction sequence involving conversion of the parent alkylarylketones into the corresponding N-cyclohexylketimines, followed by chlorination with N-chlorosuccinimide in carbon tetrachloride to afford N-cyclo-hexyl α,α-dichloroketimines, the latter compounds being hydrolyzed in acidic medium to yield the title compounds 1. The relative inaccessibility of compounds of type 1 in the literature was striking. α,α-Dichloroacetophenones 1 (R=H) are