Showing papers by "Lambert Brandsma published in 1985"

Dimetallation of phenylacetylene. Synthesis of ortho‐substituted derivatives of phenylacetylene, benzo[b]selenophene and benzo[b]tellurophene

Abstract: Phenylacetylene can be dimetallated in two ways. o-K-C6H4-C C - Li is formed by treating phenylacetylene at −70°C with two equivalents of butyllithium and one equivalent of potassium tert-butoxide in a mixture of tetrahydrofuran and hexane. The dimetallation with BuLi-N,N,N′, N′-tetramethylethanediamine (TMEDA) affords a mixture of about 15% (m + p)-Li-C6H4-C C Li and 85% o-Li-C6H4-C C-Li. Ortho-K-C6H4-C C-Li can be transformed into the dilithio or di-Grignard derivatives by addition of anhydrous lithium bromide or magnesium bromide etherate. Reaction of the dilithio derivative with elemental selenium and tellurium, followed by successive addition of tert-butyl alcohol and hexamethylphosphoric triamde (HMPT), gives benzo[b]selenophene and benzo[b]tellurophene in good yields. Regiospecific functionalization of the nucleus via dimetal derivatives succeeds in the case of alkylation, halogenation, sulfenylation and acylation (with dimethylformamide and dimethylacetamide). Trimethylchlorosilane, chloromethyl methyl ether, aldehydes and ketones do not however react regiospecifically.

Direct metallation of isoprene

Abstract: Treatment of isoprene with an excess of the couple potassium t-butoxide–lithium tetramethylpiperidide in tetrahydrofuran, followed by addition of a higher alkyl bromide or oxirane, gives the dienes H2CCHC(CH2)CH2R (R = alkyl or –CH2CH2OH) in reasonable yields.

An efficient synthesis of 1,3-thiazole

Abstract: Synthese a partir de cyclodensation de S-methyl dithiocarbamate et de chloroacetaldehyde suivie de demethylsulfenylation du methylthio-2 thiazole obtenu par reaction avec Li dans l'ammoniac liquide suivie d'hydrolyse par NH 4 Cl

Thermal Rearrangements of N-Aryl-1-alkynesulphenamides into Indoline-2-thiones

Abstract: Les sulfenamides de depart sont prepares par action de bromures d'arylamino magnesiums et d'alcyne-1yl thiocyanates; S-methylation des thiolactames obtenus par chauffage dans le benzene des sulfenamides