Synthesis of 3-substituted 2-trifluoro(trichloro)methyl-2H-chromenes by reaction of salicylaldehydes with activated trihalomethyl alkenes

Highly diastereoselective 1,3-dipolar cycloaddition of nonstabilized azomethine ylides to 3-nitro-2-trihalomethyl-2H-chromenes: synthesis of 1-benzopyrano[3,4-c]pyrrolidines

“…3-Nitro-2-trihalomethyl-2H-chromenes 1 (X¼F, Cl), prepared by tandem condensation of the appropriate salicylaldehydes with 3,3,3-trifluoro(trichloro)-1-nitropropenes, 10 have not received much attention despite their potential interest as CF 3 -and CCl 3 -building blocks in organic synthesis for the construction of trihalomethyl-containing heterocycles. The majority of the reactions with these compounds are nucleophilic additions at the 4-position leading to various types of 4-substituted chromanes.…”

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

“…We found that 3-nitro-2-(trifluoromethyl)-2H-chromenes 1aed, which are easily obtainable from the corresponding salicylaldehydes and (E)-3,3,3-trifluoro-1-nitroprop-1-ene, 13 reacted with 2-(1-phenylethylidene)malononitrile (2a) in the presence of triethylamine in dichloromethane at room temperature to give the desired 7-amino-9-phenyl-6-(trifluoromethyl)-6H-benzo [c]chromene-8-carbonitriles 3aed in 33e64% yields. In most cases, the reaction was complete after 6 h and the products could be isolated by simple filtration of the precipitate as white powders.…”

Synthesis of trans,trans-2,3,4-trisubstituted chromans from 3-nitro-2Н-chromenes and enamines of acetoacetic ester and acetylacetone. A new type of configurationally stable atropisomers

“…3-Nitro-2Н-chromenes 1a-g were obtained according to a published procedure. 16 Synthesis of chromans 3a-q and 5a-i (General method). A mixture of the appropriate chromene 1a-g (1.0 mmol) and enamine 2a-g or 4a-d (1 mmol) was heated until dissolution at 50°C in 0.2 ml of anhydrous acetonitrile (1-2 min) and maintained at room temperature for 1-2 days.…”