POCI3/DMF

Vilsmeyer-Haack formylation of 7-hydroxy-2,3,6,7-tetrahydro-l//,5//-pyrido[3,2,l-y]quinazoline-l,3-dione with POCI3/DMF gave 7-chloro-6-formyl-2,3-dihydro-l//,5// derivative. Boiling a toluene solution of the aforementioned 7-hydroxy derivative in the presence of pTSA yielded dehydrated 2,3-dihydro derivative (01MI28). 

Formylation of 5H-benzo[/]pyrrolo[l,2-d][l,4]diazepin-6(7H)-one 180 pyrrole ring with POCI3/DMF is known (Scheme 36, Section 3.1.1.1 (1992BMCL1639)). Formyation of pyrrolo-benzothiazepine can be accomplished using POCI3/ PhNMeCHO (Scheme 76 (2004JMC143)). The monoaldehyde 375 (R = H) is... 

Another synthesis of halopyridines, unique to pyridine and other IV-containing heteroarenes, involves transformation of pyridine N-oxide into the corresponding pyridone followed by halogenation. In one case, treatment of 3-chloro-2,4 -bipyridine-l -oxide (8) with acetic anhydride produced the pyridone, which was then converted to dichloride 9 with POCI3/DMF [7]. 

Treatment of B with POCI3/DMF at 100°C followed by quench with ice and dilute NaOH to give C, C14H12Q2N2O. 

Subsequent attempts to repeat this work failed. Instead, reaction of 3-pbenyl-5-isoxazolone with POCI3/DMF, first at room temperature then for 30 minutes at 60°C, gave the isoxazolone 4 in 35% yield after standard aqueous quench and neutralisation with 5% NaHC03 solution. When longer reaction times were employed, or when the reaction temperature was raised to 80°C, the product, isolated in 71% yield, was the 1,3-oxazinone 5, and 4 was shown to be the precursor to 5. 

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