Synthesis of new pterocarpans and rapid O‐alkylation under microwave irradiation

Herein, it is described five new pterocarpans. Pterocarpans 8 and 9 were synthesized by classical [3 + 2] cycloaddition reaction of 2H‐chromene 7a and 7b with 2‐methoxy‐1,4‐benzoquinone. Pterocarpan 8 was O‐alkylated in the absence of solvents using a domestic microwave oven as a heat source and a classical O‐alkylation method with traditional heating. In this way three more new pterocarpans were obtained. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:239–244, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20175     

Synthesis and reactivity of cyanomethyl 2‐amino‐4‐methylthiazolyl ketone. A facile synthesis of novel pyrazolo[5,1‐c]1,2,4‐triazine, 1,2,4‐triazolo[5,1‐c]1,2,4‐triazine, 1,2,4‐triazino[4,3‐a]benzimidazole,pyridazine‐6‐imine and 6‐oxopyridazinone derivatives

The novel and versatile cyanomethyl 2‐amino‐4‐methylthiazolyl ketone (5) was prepared by treatment of bromomethyl 2‐amino‐4‐methyl thiazolyl ketone (4) with potassium cyanide. Reaction of 5 with heterocyclic diazonium salts 6a,b and 10 afforded the corresponding hydrazones 7a,b and 11, respectively. Refluxing of the hydrazones in pyridine afforded the corresponding pyrazolo[5,1‐c]‐1,2,4‐triazine, 1,2,4‐triazolo[5,1‐c]‐1,2,4‐triazine, and 1,2,4‐triazolo[4,3‐a]benzimidazole derivatives 8a,b and 12, respectively, via intramolecular cyclization. Compound 5 coupled also with benzenediazonium chloride to afford the corresponding hydrazone 14, which is an excellent precursor for the synthesis of pyridazine‐6‐imine 17a and pyridazinone 17b. The pyridazine derivatives 17a,b were also prepared by an independent route, that is, the condensation with malononitriles and coupling with benzenediazonium chloride, followed by intramolecular cyclization. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 385–390, 1999