Transition metal-free cross-dehydrogenative arylation of unactivated benzylic C–H bonds

Abstract

The cross-dehydrogenative arylation of benzylic C–H bonds with arenes provides straightforward access to synthetically useful 1,1-diarylmethanes, from readily available starting materials. Current approaches suffer from limited substrate scope, requirement for...

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C–H Bonds Elaboration

“…75.3 to give 75.4). 505 In a related example, the same monofluorination reaction was performed under flow conditions by circulating an acetonitrile solution of 76.1 through a transparent FEP tubing coiled around a glass cylinder (V = 28 mL, flow rate = 1 mL• min −1 ) containing a 105 W CFL. 287 Under these conditions, it was found that XA (5 mol %) could perform the monofunctionalization of the benzylic site to get 76.3 in 89% yield with a residence time of 28 min (temperature of the system = 40 °C).…”

“…More recently, the above-mentioned procedure for the monofluorination of alkylaromatics was used to develop a one-pot, transition metal-free cross-dehydrogenative arylation of unactivated benzylic C–H bonds (Scheme ). In particular, FL was used to trigger the halogenation step, while the so-formed benzyl fluorides ( 75.2 ) were used as electrophilic partners in a nucleophilic substitution with electron-rich (hetero)­arenes (e.g. 75.3 to give 75.4 ) …”

“… In particular, FL was used to trigger the halogenation step, while the so-formed benzyl fluorides ( 75.2 ) were used as electrophilic partners in a nucleophilic substitution with electron-rich (hetero)­arenes (e.g. 75.3 to give 75.4 ) …”

Visible-light-promoted generation of p-(N,N-dimethyl)benzyl equivalents and their reactions with quinols: easy access to diarylalkanes

“…Firstly, trifluoromethyl-containing naphthaquinol 1a was selected as the acceptor of the benzyl equivalents (Table 1) as trifluoromethylcontaining quinols showed excellent reactivity toward the synthesis of trifluoromethylated arenes (Scheme 1b). [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] Visiblelight promoted the construction of 1,1-diarylmethanes, which was initially investigated by the reaction of 1a with N,Ndimethyl aniline 2a in the presence of a photosensitizer, Ir( ppy) 3 (1 mol%), in acetonitrile (CH 3 CN, 2 mL) without any other additives under 15 W blue LED irradiation at room temperature (Table 1, entry 1); this reaction produced diarylalkane 3a in 42% isolated yield. The yield of 3a was improved to 47% when [Ir(dtbbpy)( ppy) 2 ][PF 6 ] was used as the photosensitizer (Table 1, entry 2).…”

“…15,31,[40][41][42][43] It was shown that 1,1-diarylmethane is a useful motif that is usually found in natural and bioactive compounds, such as bifemelane, benproperine, and tolterodine (Fig. 1), 44,45 which could be synthesized from acid-promoted Friedel-Crafts benzylation or transition-metal catalyzed cross-dehydrogenative benzylic arylation, etc. [46][47][48][49] These strategies generally require substrates with an α-activating group at the benzylic position or an additional base, oxidant, or radical initiator for activation.…”