Vladimir S. Moshkin

Novel data for the reaction of 3-cyano-(thio)chromones with N-nucleophiles

Recent literature data for the reaction of 3-cyano(thio)chromones with amines, hydrazines, and hydroxylamine are summarized.

Synthesis of 4-aryl-6-methyl-7a-(trifluoromethyl)-2,4a,5,6,7,7a-hexahydropyrano[2,3-c]pyrrol-2-ones from 4-aryl-6-(trifluoromethyl)-2-pyrones, sarcosine, and formaldehyde

4-Aryl-6-(trifluoromethyl)-2-pyrones reacted with the nonstabilized azomethine ylide obtained from sarcosine and formaldehyde under reflux in benzene for 6 h, resulting in [3+2] cycloaddition that gave 4-aryl-6-methyl-7a-(trifluoromethyl)-2,4a,5,6,7,7a-hexahydropyrano-[2,3-c]pyrrol-2-ones in 42–56% yields. In the case of 4-aryl-3-carbethoxy-6-(trifluoromethyl)-2-pyrones, besides the respective pyrano-[2,3-c]pyrrolidines (66–71% yields) also 4-aryl-1-methyl-2-(trifluoromethyl)pyrroles were isolated as minor products.

A novel synthesis of (E)-1-(2-hydroxyphenyl)-3-(1Н-indol-3-yl)- prop-2-en-1-ones from chromone-3-carboxylic acid and indoles

The reaction of chromone-3-carboxylic acid with indoles in boiling ethanol proceeds as a 1,4-nucleophilic addition with successive opening of the pyrone ring and decarboxylation to afford a series of previously unknown trans-indolyl chalcones in 27–60% yields.

(3+2) Cycloaddition of N-methylazomethine ylide obtained from sarcosine and formaldehyde to CH- and NH-acidic enones and enamides

Conjugated unsaturated carbonyl compounds with weak CH or NH acidity were used in a three-component reaction with sarcosine and formaldehyde, forming (3+2) cycloaddition products in 32–73% yields. The conversion was estimated from NMR data and strongly depended on the acidity of dipolarophile and the steric accessibility of its double bond.

Synthesis of 2-amino-6-oxo-5-salicyloyl-1,6-dihydropyridine- 3-carboxamides from 3-carbamoylchromones and cyanoacetamides

3-Carbamoylchromones reacted with cyanoacetamides in the presence of sodium ethoxide in refluxing ethanol, forming 2-amino-5-aroyl- 6-oxo-1,6-dihydropyridine-3-carboxamides in 50–88% yields.

Reaction of 3-cyanochromones with pyridinium phenacylide

The reaction of 3-cyanochromones with Nand C-nucleophiles begins with an attack at C-2 atom with subsequent opening of the γ-pyrone ring and recyclization at the C=O or C≡N groups [1-3]. Nucleophilic 1,2-addition at the cyano group usually does not occur [1], while the reactions with aromatic amines [4] and methylenetriphenylphosphorane (Ph3P=CH2) [5] terminate at the stage of open products 1 and 2. Since the assumption of a number of workers of possible addition of nucleophiles at the cyano group was subsequently shown to be incorrect [1], the reports in the literature on the synthesis of azirines 3a,b from the corresponding 3-cyanochromones 4a,b and pyridinium phenacylide [6] are cast in doubt and require verification.