Péter Ábrányi-Balogh

Microwave-assisted synthesis of thioamides with elemental sulfur

Thioamides are valuable intermediates in organic chemistry (1). Moreover, this functional group constitutes an important part of some pharmacophores with widespread applications (2).A number of methods have been reported in the literature for the preparation of thioamides. In general, they were synthesized from the corresponding nitriles using thioacetic acid (3), O,O-dialkyl dithiophosphates (4), diphenylphosphinodithioic acid (5), sodium trimethylsilanethiolate (6), Dowex SH (7), or sodium hydrogen sulfide/diethylamine hydrochloride (8) as the reagent. Thioamides have also been prepared from amides, reacting them with tetraphosphorus decasulfide, either with or without additives (9), or using Lawesson’s reagent (10), ethylaluminum sulfide (11), or boron sulfide (12). Another method for the synthesis of thioamides utilizes elemental sulfur in the Willgerodt–Kindler reaction involving amines and aldehydes or ketones (13). Sulfur as a simple, inexpensive, and versatile reagent has been used in numerous organic transformations in the past several years (14). Our aim was to study the reaction of a variety of arylmethylamine derivatives with elemental sulfur under microwave (MW) conditions.

Practical Synthesis of 6-Chloro-dibenzo[c.e][1,2]oxaphosphorine

Abstract The title P-heterocycle 3, a versatile intermediate in synthesis, was prepared by two independent methods. The first involves an environmentally friendly version of an old protocol starting from 2-phenylphenol (1) and phosphorus trichloride. Their interaction could be accomplished at 50 °C under solventless conditions. Cyclization of the intermediate (2) so obtained could be realized best under microwave conditions at 150 °C in the presence of ZnCl2. This method offers advantages over the traditional ones. According to another approach, the chloro-dibenzooxaphosphorine (3) was obtained by the novel reaction of 6H-dibenzo[c.e][1,2]oxaphosphorine-6-oxide (4) with phosphorus trichloride in boiling chloroform. Efficiency of the syntheses was demonstrated by converting the crude product 3 to a more stable phosphonic amide (6) that was stable enough to be isolated.

Microwave-assisted amidation of arylacetic acids by reaction with 2-aryl-ethylamines

Abstract Twenty-five amides were synthesized in almost quantitative yields by microwave-assisted condensation of arylacetic acids and 2-aryl-ethylamines under solventless conditions. The N-arylethyl-arylacetylamides are intermediates of the corresponding isoquinoline derivates. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

A Study on the Phosphorylation of Indole, Imidazole, Carbazole, and Phenothiazine Derivatives

Abstract N-Heterocycles including indolecarbaldehyde, substituted benzimidazoles, and methylimidazole could be efficiently phosphorylated by diethyl chlorophosphate at room temperature in different solvents using alkali carbonate or triethylamine as the base. However, the phosphorylation of N-heterocycles with a lower reactivity at the NH function, such as carbazole and phenothiazine, could not be conducted to complete conversion under the conditions applied.

Milestones in microwave-assisted organophosphorus chemistry

GRAPHICAL ABSTRACT ABSTRACT The microwave (MW) technique become an important tool in organophosphorus chemistry. On the one hand, otherwise reluctant reactions, such as the Diels–Alder cycloadditions, inverse Wittig-type reactions, esterification of P-acids, alcoholysis of P-esters, may be promoted on the effect of MW, while on the other hand, catalysts may be omitted, or catalyst systems may be simplified on MW irradiation. This later group includes the Kabachnik–Fields and the Pudovik reactions, deoxygenation, as well as the Hirao- and the Arbuzov reactions.

Total synthesis of racemic 1-aryl-tetrahydroisoquinoline alkaloids

A new synthetic route was developed for the preparation of natural products cryptostyline I, II, III and 1-phenyl-6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinoline. The Liebeskind–Srogl palladium-catalyzed carbon–carbon cross-coupling protocol was used in the key step of the total synthesis.Graphical abstract