Bromofluorination of Alkenes: 1‐Bromo‐2‐Fluoro‐2‐Phenylpropane

Abstract

Bromofluorination of alkenes: 1‐bromo‐2‐fluoro‐2‐phenylpropane product: 1‐Bromo‐2‐fluoro‐2‐phenylpropane

Synthesis of optically active 2-fluoroalk-1-en-3-yl esters and chirality transfer in their Claisen-type rearrangements

“…Lipasecatalyzed transesterification of the fluorinated allylic alcohols 1 with vinyl acetate in organic medium was superior over the hydrolysis in a phosphate buffer of corresponding acetates 2. The former acetylation gave (S)-(À)-3-acetoxy-2-fluoroalk-1-enes, (S)-(À)-2a-c, of chain lengths C 10 , C 16 and C 18 with 68-89% yield and 92-96% ee, while the remaining (R)-(+)-2-fluoroalk-1-en-3-ols, (R)-(+)-1a-c, were isolated with 54-96% yield and 72-86% ee. Thus, the enantiopreference for the fluorinated allylic alcohols was that predicted by the Kazlauskas rule for the selectivity of serine proteases.…”

“…According to our earlier investigations we prepared 2-fluoroalk-1-en-3-ols (1a-c) by bromofluorination [15,16] of terminal alkenes, subsequent HBr elimination from the formed 1-bromo-2-fluoroalkanes [17][18][19][20] and allylic hydroxylation of the resulting vinyl fluorides with substoichiometric selenium dioxide and tert-butylhydroperoxide in the presence of catalytic amounts of acetic acid (Scheme 2) [20].…”

Claisen rearrangements based on vinyl fluorides

“…Similar to the procedure mentioned above, (E)-1-fluorocyclododecene (21) was prepared from diastereopure cis-1-bromo-2-fluorocyclododecane (20) [43,44] (13.25 g, 50.0 mmol) by refluxing with KO t Bu (11.23 g, 100 mmol) in cyclohexane (650 mL) for 5 h. Yield: 9.02 g (98%). The spectroscopic data agree with published ones [66].…”

“…In the frame of our interest in synthetic applications of vinyl fluorides, we discovered a simple and efficient access to 2-fluoroallylic alcohols some years ago consisting of bromofluorination of terminal alkenes [43,44], dehydrobromination of the formed 1-bromo-2-fluoroalkanes [45][46][47] and SeO 2 -mediated allylic oxidation [48]. Now we investigated the application of these fluorinated allylic alcohols in different types of Claisen rearrangements.…”

Bromofluorination of unsaturated compounds using DMPU/HF as a fluorinating reagent

“…Existing synthetic strategies to effectively pursue bromofluorination of alkenes relied on utilizing different reagents such as tetrabutylammonium bifluoride [6] and BrF 3 [7]. It has been shown that the combination N-bromosuccinimide (NBS) and triethylamine trihydrofluoride (Et 3 N/3HF) was an efficient way of producing bromofluoro compounds from alkenes [8]. In this case, NBS was acting as electrophilic bromine source and Et 3 N/3HF is the nucleophilic fluorinating specie.…”