Chromone-2-carbonyl azides

Chromone-2-carbonyl azide (67) may be prepared in excellent yield either by adding sodium azide to a solution of the acyl chloride (68) in dioxan, or by the action of nitrous acid on the hydrazide (69) [157], A Curtius reaction on the azide led to an interesting series of derivatives of 2-aminochrbmone (70, R = OEt, Me, CCI3, NEta and similar groups), whose reactions have been studied [175-179]. 

Another conversion of a chromone to a coumarin proceeds through chromone-2-carbonyl azide and either the amide (94, R = CCI3) or the urea (95) hydrolysis of either of these gives 4-hydroxycoumarin (9(S) [157]. The amide (94, R = CCI3 or OEt) reacts with a primary alkylamine and a twofold molar quantity of formaldehyde to form a reduced chromono [3,2-c]pyrimidine (97) [176]. 

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See also in sourсe #XX -- [ , ]

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