C-H Bond Functionalization via Hydride Transfer: Formation of 浼?Arylated Piperidines and 1,2,3,4-Tetrahydroisoquinolines via Stereoselective Intramolecular Amination of Benzylic C-H Bonds was written by Vadola, Paul A.;Carrera, Ignacio;Sames, Dalibor. And the article was included in Journal of Organic Chemistry in 2012.Safety of Methyl 2-bromo-4-fluorobenzoate This article mentions the following:
We here report a study of the intramol. amination of sp3 C-H bonds via the hydride transfer cyclization of N-tosylimines (HT-amination). In this transformation, 5-aryl aldehydes are subjected to N-toluenesulfonamide in the presence of BF3璺疧Et2 to effect imine formation and HT-cyclization, leading to 2-arylpiperidines and 3-aryl-1,2,3,4-tetrahydroisoquinolines in a one-pot procedure. We examined the reactivity of a range of aldehyde substrates as a function of their conformational flexibility. Substrates of higher conformational rigidity were more reactive, giving higher yields of the desired products. However, a single substituent on the alkyl chain linking the N-tosylimine and the benzylic sp3 C-H bonds was sufficient for HT-cyclization to occur. In addition, an examination of various arenes revealed that the electronic character of the hydridic C-H bonds dramatically affects the efficiency of the reaction. We also found that this transformation is highly stereoselective; 2-substituted aldehydes yield cis-2,5-disubstituted piperidines, while 3-substituted aldehydes afford trans-2,4-disubstituted piperidines. The stereoselectivity is a consequence of thermodn. control. The pseudoallylic strain between the arene and tosyl group on the piperidine ring is proposed to rationalize the greater stability of the isomer with the aryl ring in the axial position. This preferential placement of the arene is proposed to affect the observed stereoselectivity. In the experiment, the researchers used many compounds, for example, Methyl 2-bromo-4-fluorobenzoate (cas: 653-92-9Safety of Methyl 2-bromo-4-fluorobenzoate).
Methyl 2-bromo-4-fluorobenzoate (cas: 653-92-9) belongs to organobromine compounds. Organo bromine compounds are versatile compounds and are widely used in diverse fields. Organo bromine derivatives are used in the dye sector, as an indicator in analytical chemistry (Bromothymol blue is a popular indicator). Many of the alkyl bromine derivatives are excellent alkylating agents since bromides are good leaving groups. Tribromides, like tetrabutylammonium tribromide, are used as a solid source of bromine. N-bromosuccimide (NBS) is used for the selective bromination of allylic bonds.Safety of Methyl 2-bromo-4-fluorobenzoate
Referemce:
Bromide – Wikipedia,
bromide – Wiktionary