Benzodiazines: recent synthetic advances.

Benzodiazines (diazonaphthalenes with both nitrogens in the same ring) - cinnolines (1,2-benzodiazine), quinazolines (1,3-benzodiazine), phthalazines (2,3-benzodiazine) and quinoxalines (1,4-benzodiazine) - are important class of compounds with broad biological properties and wide application in pharmaceutical as well as agrochemical arenas. These diazaheterocycles are present in a wide variety of bioactive natural products as well as synthetic molecules that are good drug candidates constituting key structural units responsible for their pronounced therapeutic activities. Their rapidly growing uses and applications in medicinal and agrochemical arenas prompt the researchers for further studies on this important group of compounds. In this review, we hope to provide a brief overview of the important general methodologies and recent developments towards their synthesis and open the door for further progress in this area.

Superelectrophilic Activation of Crotonic/Methacrylic Acids: Direct Access to Thiochroman-4-ones from Benzenethiols by Microwave-Assisted One-Pot Alkylation/Cyclic Acylation.

An efficient microwave-assisted protocol for the synthesis of 2-/3-methylthiochroman-4-ones by superacid-catalyzed alkylation followed by cyclic acylation (cyclization via intramolecular acylation) is described. Using easily accessible benzenethiols and crotonic acid/methacrylic acid with triflic acid (as catalyst of choice for needed optimal acidity), the reaction was tuned toward the formation of the cyclized products in good selectivity and yield. A mechanism involving the formation of carbenium-carboxonium superelectrophilic species is suggested.

Fluoroanalogs of DDT: superacidic BF3-H2O catalyzed facile synthesis of 1,1,1-trifluoro-2,2-diarylethanes and 1,1-difluoro-2,2-diarylethanes.

The one-pot synthesis of 1,1,1-trifluoro- and 1,1-difluoro-2,2-diarylethanes from arenes and fluorinated hemiacetals in the BF(3)-H(2)O system is described. The reaction is simple, clean, and convenient, eliminating the use of organic solvents and other expensive acid systems. BF(3)-H(2)O is economic, is easy to prepare, and offers ample acidity required for this reaction.

Preparation of trifluoromethylated dihydrocoumarins, indanones, and arylpropanoic acids by tandem superacidic activation of 2-(trifluoromethyl)acrylic acid with arenes.

Indanones and coumarins are important intermediates for the convenient synthesis of many pharmaceutical and biologically active compounds. Fluoroorganics play a vital role in the design of very effective therapeutics due to significant enhancenment in their lipophilicity, bioavailability, and fast uptake by the presence of fluorine in these molecules. Herein, we report an efficient one-pot synthesis of trifluoromethylated arylpropanoic acids, indanones, and dihydrocoumarins using Friedel-Crafts alkylation or tandem Friedel-Crafts alkylation-cycloacylation of arenes/phenols with 2-(trifluoromethyl)acrylic acid under superacidic conditions using trifluoromethanesulfonic acid. The results have been rationalized by the structure energy calculations of the involved reaction intermediates using ab initio theoretical methods.