Ni-Catalyzed Radical-Promoted Defluoroalkylborylation of Trifluoromethyl Alkenes To Access gem-Difluorohomoallylic Boronates

Abstract

gem-Difluoroalkenyl boronates are attractive synthons for constructing diverse gem-difluoroalkenes and organoboron compounds. However, the strategies for the construction of gem-difluorohomoallyl boronates has scarcely been described. Herein, we develop an efficient protocol for the construction of gem-difluorohomoallylic boronates through a Ni-catalyzed radical-promoted defluoroalkylborylation of α-trifluoromethyl alkenes with α-haloboronates under mild conditions. This reaction features a broad substrate scope with good functional group tolerance and diverse transformations.

Defluorinative Alkylation of Trifluoromethyl Alkenes with Soft Carbon Nucleophiles Enabled by a Catalytic Amount of Base

“…Meanwhile, catalytic variants by virtue of transition metals, [6] photoredox, [7] and electrochemical [8] technique were also described to enable the incorporation of diversified functional groups attached to gem ‐difluoroalkenes through β‐F elimination of TAs. In the historical context of synthesizing alkyl substituted gem ‐difluoroalkenes, existing protocols usually relied on the pre‐functionalized alkyl group progenitors as the coupling partners, such as halides, [6c,i,j,7f–i,8a,b] acetals, [6d] oxime ethers, [6e,7e] carboxylates, [6h,7b–d,8c] trifluoroborates, [7a] etc (Figure 1a). Notwithstanding these achievements, the exploration of efficient and operationally mild strategies that avoid the use of organometallic reagents, strong bases, and transition metals, and install a densely functionalized alkyl group to gem ‐difluoroalkenes that permits further elaborations is highly sought‐after.…”

KIO3-Mediated γ-C(sp3)–H Sulfenylation of Enaminones

“…It should be noted that the ubiquitously lower yield of substrates with an electrondonating group compared to those with an electron-withdrawing group highlights the sensitivity of the electronic effect on arene. 10 Other substitutents, such as methyl (3e), ester (3g), and methylenedioxy (3n), were well tolerated, giving the products in good yields (69−84%). In addition, the enaminones derived from heteroaromatic systems, including furan (3s), thiazole (3t), and pyridine (3u), cloud be employed as well.…”

“…Although substrates with strong electron-donating groups such as methoxyl ( 3f , 3q ) were less reactive, reactions of these substrates still provided products in moderate yields (59% and 53%, respectively). It should be noted that the ubiquitously lower yield of substrates with an electron-donating group compared to those with an electron-withdrawing group highlights the sensitivity of the electronic effect on arene . Other substitutents, such as methyl ( 3e ), ester ( 3g ), and methylenedioxy ( 3n ), were also well tolerated, giving the products in good yields (69–84%).…”

Transition-metal-free oxidative annulation reactions between N-acyl-2-aminoacetophenones and alkynes for the facile synthesis of 2-amino-1-naphthols

“…A variety of solvents (Table 1, entries 2–4) and oxidants (Table 1, entries 5–6) were subsequently examined, and the results showed a decrease in the reaction yield. Subsequently, the yield of 3a could be improved by the addition of 2.0 equivalents of lithium chloride (LiCl) as the additive 10 (Table 1, entry 7). Gratifyingly, when the reaction temperature was decreased from 140 °C to 120 °C, the yield of 3a was effectively increased to 61%.…”