The solid-state reaction between anilines and phenacyl bromides in the presence of an equimolecular amount of sodium bicarbonate gives N-phenacylanilines. Microwave irradiation of mixtures of these compounds with anilinium bromides at 540 W for 45-60 s provides a mild, general, and environmentally friendly method for the synthesis of 2-arylindoles in 50-56% overall yields. A onepot variation of the method, involving irradiation of 2:1 mixtures of anilines and phenacyl bromides, was also developed, allowing a simplified experimental procedure and leading to improved yields (52-75%).

Reactions between 1-dimethylamino-1-azadienes and several quinones in the presence of a chloroformyl polystyrene resin proceeded with up to 2.5-fold increase in the isolated yields of the hetero Diels-Alder products, owing to efficient scavenging of dimethylamine liberated from the primary cycloadducts.

Microwave irradiation leads to a considerable improvement of the cyclocondensation between anthranilic acid and lactim ethers derived from piperazine-2,5-diones in terms of reaction times, yields, and stereocenter integrity. This reaction has been used to prepare some derivatives of the pyrazino[2,1-b]quinazoline-3,6-dione system present in many quinazoline alkaloids. It could also be applied to the synthesis of compounds containing the complete hexacyclic ring system of the anti-MDR natural product N-acetylardeemin, and other comprising the pentacyclic framework of circumdatin E. The microwave-assisted reaction was also much better than the thermal one when applied to a bis-lactim ether, leading to the corresponding pentacyclic pyrazino[2,1-b:5,4-b¢]diquinazoline-8,16-dione in excellent yield.

A general, efficient and environmentally friendly procedure for the synthesis of 2,5-piperazinediones is described, involving the microwave irradiation of N-Boc dipeptide esters.

Microwave irradiation greatly improves the results of the cyclocondensation between anthranilic acid and lactim ethers derived from 2,5-piperazinediones in terms of reaction times, yields and stereocenter integrity, leading to pyrazino[2,1-b]quinazoline-3,6-diones. The microwave-assisted reaction was also much better than the thermal one when applied to a bis-lactim ether, leading to the corresponding pentacyclic pyrazino [2,1-b:5,4-b¢]diquinazoline-5,13-dione in excellent yield, and it also improved the preparation of compounds containing the ring system of the anti-MDR natural product N-acetylardeemin.