Tetrahedron report number 221

Innate C-H trifluoromethylation of heterocycles

Direct methods for the trifluoromethylation of heteroaromatic systems are in extremely high demand in nearly every sector of chemical industry. Here we report the discovery of a general procedure using a benchtop stable trifluoromethyl radical source that functions broadly on a variety of electron deficient and rich heteroaromatic systems and demonstrates high functional group tolerance. This C-H trifluoromethylation protocol is operationally simple (avoids gaseous CF(3)I), scalable, proceeds at ambient temperature, can be used directly on unprotected molecules, and is demonstrated to proceed at the innately reactive positions of the substrate. The unique and orthogonal reactivity of the trifluoromethyl radical relative to aryl radicals has also been investigated on both a complex natural product and a pharmaceutical agent. Finally, preliminary data suggest that the regioselectivity of C-H trifluoromethylation can be fine-tuned simply by judicious solvent choice.

Synthesis and in vitro cytotoxicity evaluation of some fluorinated hexahydropyrimidine derivatives

A series of trifluoromethylated hexahydropyrimidine and tetrahydropyrimidine derivatives were synthesized and their in vitro cytotoxic activities were determined in colon cancer cell line (COLO 320 HSR). Compounds 4f, 4g, 4k, 5, and 7 proved to be the most active in this series of compounds. They represent promising new leads for the development of highly potent and selective anticancer compounds. All the compounds are lipophilic due to the trifluoromethyl group, and are thus expected to penetrate the membrane in appreciable concentration.

Synthesis of novel 1-[(2,6-dichloro-4-trifluoromethyl)phenyl]-3-aryl-1H-pyrazole-4-carbaldehydes

A series of novel 1-[(2,6-dichloro-4-trifluoromethyl)phenyl]-3-aryl-1H-pyrazole-4-carbaldehydes 6a-i were synthesized using the Vilsmeier-Haack reagent. The structures of all the title compounds have been confirmed by elemental analysis, ¹H-NMR and ¹³C-NMR and in addition, the structure of intermediate 5b was investigated by X-ray crystallography.

Diastereoselective synthesis of 2-fluoroaziridine-2-carboxylates by Reformatsky-type aza-Darzens reaction

The reaction of ethyl dibromofluoroacetate with imines using zinc metal gave 2-fluoroaziridine-2-carboxylates via aza-Darzens reaction of the primary product of the Reformatsky reaction with high diastereoselectivity in excellent yields (quantitative yield and Dr = 85:15). This chemoselective formation of 2-fluoroaziridines was achieved by using CH₃CN as a solvent. Interestingly, the reaction proceeded without activation of zinc metal, which was necessary for the Reformatsky reaction of bromodifluoroacetate. None of α-bromo-α-fluoro-β-lactams, four-membered cyclization products, and noncyclized 3-amino-2-bromo-2-fluorocarboxylic esters, usual Reformatsky adducts, were formed.