2.4- Diaryl-3,4-dihydro-277-pyrido

Reaction of 2-(arylmethyleneamino)pyridines 335 and styrenes in the presence of hydroquinone afforded 2,4-diaryl-3,4-dihydro-2/f-pyrido[l,2-n]pyrimidines 336 by means of an inverse electron demand Diels-Alder reaction (95MI10). Reaction of 2-(benzylideneamino)pyridines 337 and chloroacetyl chloride gave 2-aryl-4//-pyrido[l,2-n]pyrimidin-4-ones 338 (97JMC2266). 

Reaction of coumarinoyl hydrazides 213 and 3-methyl-2,3-dihydro-7-oxo-7H-pyrido[l,2,3-de][l,4]benzoxazine-5-carboxylic chlorides 212 in the presence of H2NS03H in DMF at 125 °C for 4-5 h, or under microwave irradiation for 4-5 min afforded 2,5-diaryl-l,3,4-oxadiazines 214 in excellent yields (09JHC289). 

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