Chemoselective Bromination of Dienoates

Abstract

A variety of tetra‐, di‐ and monobromo derivatives of dienoates were prepared from parent polyunsaturated esters under mild conditions. According to proposed protocol the target bromoesters were easily obtained as a rule in good yields and high selectivity.

2-Aryl-6-Polyfluoroalkyl-4-Pyrones as Promising RF-Building-Blocks: Synthesis and Application for Construction of Fluorinated Azaheterocycles

“…As mentioned above, the cyclic pyranic form B was observed in the bromination reaction mixtures ( Table 2 ), whereas bromoenones A were detected by NMR spectroscopy on the treatment of the dibromo derivatives 3 with pyridine at room temperature. The easy formation of 2-bromoenones from 2,3-dibromoketones is also well presented in the literature [ 42 ]. Thus, it can be assumed that the first path is more preferable in basic conditions.…”

“…The introduction of the strong electron-donating substituent (4-Me 2 N) led to preferential bromination at the aromatic ring rather than at the double bond followed by cyclization because of basic properties of the substituent ( Scheme S1 in Supplementary Materials ). It should be noted that, in all cases, compounds 3 were formed as a sole anti -dibromo diastereoisomer according to the classical concept of electrophilic addition of bromine to alkenes via the cyclic bromonium cation [ 42 ].…”