Microwave-assisted Solventless Condensations

Hassan, V, Abbas, S. 2005. An efficient procedure for the synthesis of coumarin derivatives using TiCl4 as catalyst under solvent-free conditions. Tetrahedron Lett. 46 3501-3503. Helavi, B. V, Solabannavar, S. B., Salunkhe, R. S., Mane, R. B. 2003. Microwave-assisted solventless Pechmann condensation. J. Chem. Res. 5 279-280. 

An efficient microwave-assisted multi-step synthesis of8//-quinazolino [4,3-b] quina-zolin-8-one has been investigated by Besson and co-workers77. The synthesis involved two Niementowski condensations starting from substituted anthranilic acids (Scheme 3.49). Both homogeneous and heterogeneous conditions were studied in an effort to develop a convenient synthesis of the desired compounds. The solventless procedure allowed easier access to the quinazolino[4,3-fi]quinazolin-8-ones and gave better yields than the method performed in the presence of solvents. However, the procedure with solvents would offer the possibility of investigating the microwave-assisted solid-phase synthesis of these quinazolinones, which would faciltate purification of the final products. 

Solventless, Microwave-Assisted Synthesis of Coumarins via a Tandem Knoevenagel Condensation and an Intramolecular Nucleophilic Acyl Substitution... 

Kappe CO, Kumar D, Varma RS (1999) Microwave-assisted high-speed parallel synthesis of 4-Aryl-3,4-dihydropyrimidin-2(lH)-ones using a solventless biginelli condensation protocol. Synthesis 10 1799-1803... 

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