Chromone-2-carbonitriles

Some unsaturated nitriles undergo photoaddition to alkenes to form [3+2] cycloadducts through a 1,4-biradical intermediate. This type of reaction occurs when chromone-2-carbonitrile and an excess of isobutene in methanol are irradiated the imine (113) is formed together with a smaller amount of the nitrile (114).120 Chromone-3-carbonitrile is converted into the benzopyrano[2,3-b]pyridine (115) by heating with benzoylglycine and sodium acetate-acetic... 

Nitriles are easily hydrolysed to the corresponding carboxylic acid, and 2-cyanochromone (chromone-2-carbonitrile) undergoes this transformation when heated with sulphuric acid [113], but the yield has not been published since the best route to a 2-cyanochromone [57] begins with the chromone-2-carboxylic ester, hydrolysis of nitriles cannot at present be considered a useful method of preparing chromone-2-carboxylic acids. 

Chlorocoumarin-3-carbonitrile can undergo reaction with aminothiazoles, aminopyrazoles, and aminotriazoles under basic conditions to give the fused azolopyrimidines 173 (Equation 43) <2002HC0129>. Similar ring systems can also be obtained by the reaction of an aminopyrazole with the bis-chromone 174 (Equation 44) <2003HC0615>. 

Chromone-3-carbonitrile oxide obtained from 3-formylchromone oxime by bromination and subsequent dehydrobromination underwent cycloaddition reactions with terminal alkenes to give isoxazolines 34 (175). 

The acid chloride of 0-acetylsalicyIic acid reacts with the lithium etiolate of acetone or butan-2-one to give a chromone in good yield. The same substrate is converted into a 2-aminochromone-3-carbonitrile by heating with malono-nitrile (review [2073]) and alkali. 

Chromone-3-carbonitrile reacted with various hydrazines and reactive methylene compounds to form benzopyrano[4,3-c]pyrazoles or 4-(2-hydroxybenzoyl)-1-phenylpyrazoles and benzopyrano[2,3-6]pyridines. Preferential electrophilic attack at C-5 of 6-substituted chromones (and coumarins) has been demonstrated again by a Fischer indolization of ethyl 6-hydrazinochromone-2-carboxylate (173) to give (174) in good yield. 

Recently, Sosnovskikh et al. reported that 2-(trifluoromethyl)chromones 130 reacted with two molecnles of ethyl cyanoacetate, yielding benzo[c]chromene-8-carbonitriles... 

Reactions of chromones 230 with acetoacetamide and ethyl acetoacetate in ethanol in the presence of ammonium acetate proceed at the C-2 atom of the chro-mone system with pyrone ring-opening and subsequent cycUzation to 252. Similar reaction with p-aminocrotononitrile gave 5-hydroxy-2-methyl-5-(polylluoroalkyl)-5ff-chromeno[4,3- ]pyridine-3-carbonitriles (253a) [129]. Three-component reaction between chromones 230, dimedone, and AcONH, is accompanied by detrifluoroacetylation and leads to 254 in low yields [130] (Schane 82). 

Klutchko S, Brown RE, Von Strandtmann M (1976) Substituted chromone-3-carbonitriles, carboxamides and carboxylic acids usefttl for preventing asthmatic symptoms. US 3937837... 

---