Developments in the Chemistry of α‐Carbonyl Alkyl Bromides

Abstract

α-Carbonyl alkyl bromides are powerful reactive species for the formation of carbon-carbon bonds. Strategies relying on intermolecular C-H functionalization and cross-coupling reactions, also referred to as intramolecular cyclization, have been employed for the construction of alkenes, alkanes, ketones, and other natural-product-like ring compounds from simple alkynes, alkenes, and 1,n-enynes. In view of the importance of these α-carbonyl alkyl bromides, especially the difluoro carbonyl alkyl bromides, many researchers have focused their efforts to develop facile and mild synthetic methods for compounds with important biological activities. This review aims to briefly discuss the latest developments in the transformation of α-carbonyl alkyl bromides with emphasis on the related reaction mechanisms.

TEMPO‐Mediated Synthesis of N‐(Fluoroalkyl)imidazolones via Reaction of Imidazoles with Iodofluoroacetate

“…These results indicate that TEMPO plays a key role in the transformation. To compare these results with the effect of traditional oxidants, K 2 S 2 O 8 , Oxone and TBHP were employed in the reaction, but use of these oxidants resulted in much lower yields of the desired product (12%, 8%, and 54%, respectively; Table 1, Entries [16][17][18]. Air can be used as a green oxidant, [15] and so the reaction was conducted in the presence of CuBr 2 and air to provide the target product 3 in 36% yield ( The reaction scope was studied with these optimized conditions in hand.…”

“…The resulting Cu (I) species could be reoxidized to Cu(II) via conversion of TEMPO to 2,2,6,6-tetramethylpiperidin-1-olate B. Under heating conditions, iodofluoroacetate 2 a may undergo mesolytic cleavage of the CÀ I bond to afford a radical C, [17] which then undergoes radical addition with 1 a and TEMPO to form intermediate 32. [18] Radical…”

Hybrid Reaction Systems for the Synthesis of Alkylated Compounds Based upon Cu‐Catalyzed Coupling of Radicals and Organometallic Species

“…Difunctionalization of unsaturated C-C bonds is a useful approach for the synthesis of complex functionalized aliphatic compounds in one step. [28] This difunctionalization system is similar to ATRA (atom-transfer radical addition) reactions catalyzed by a copper salt. For example, chloro-thiolation of alkyne 19.1 to give chlorothiolated alkene 19.3 is catalyzed by a copper catalyst in the presence of stoichiometric amounts of PPh 3 and sulfonyl chloride 19.2 (Scheme 19).…”

Recent Advances in Silver‐Mediated Radical Difunctionalization of Alkenes

“…Readily available α ‐carbonyl alkyl bromides have emerged as efficient substrates for providing alkyl radicals to initiate the transition metals‐catalyzed intermolecular 1,2‐difunctionalization with alkenes [46] …”