Ligand- and Substrate-Controlled para C–H Borylation of Anilines at Room Temperature

C–H borylation: a tool for molecular diversification

“…Concurrently, we reported 123 another para -borylation of ortho -substituted anilines using the 2 nd generation defa ligand ( L7 ) (Fig. 41).…”

“…23). In this total synthesis, they performed a sterically directed C-H borylation using the Ir-dtbpy system on (122) to achieve a 93% yield of the borylated product (123). Next, a Pd-catalyzed alkenylation and further treatment resulted in the target products (125) and (126).…”

Remote Steric Control for Site-Selective Synthesis

“…11 Interestingly, the authors suggested that the geometry of the ligand may play an important role by enhancing the interaction with the bulky aluminum cocatalyst, in a similar manner to the remote steric control strategies discussed in the next sections. Smith and Maleczka, 12 and Chattopadhyay 13 reported that an aniline substrate is converted in situ into ArNRBpin under the C-H borylation conditions using B 2 Pin 2 , and that the Bpin group on aniline creates a steric shield by intramolecular hydrogen bonding with the adjacent C-H, resulting in high para-selectivity. Smith and Maleczka, 14 and Phipps 15 found that sulfate and sulfamate salts derived from phenols, benzyl alcohols, anilines, or benzyl amines bearing a bulky ammonium cation underwent selective para-borylation by blocking both the ortho-and meta-positions.…”

Borylation directed borylation of N-alkyl anilines using iodine activated pyrazaboles

“…3 Directing groups generally are required for this ortho C–H borylation as in the absence of DGs the electrophilic C–H borylation of anilines leads to para -functionalisation, 4 while iridium and cobalt catalysed C–H borylations generally lead to mixtures of meta - and para -borylated products. 1 b ,5 To date, the ortho C–H borylation of anilines has been dominated by approaches requiring the separate installation and removal of a directing group (resulting in “multiple pot” processes). 6,7 For example, the electrophilic ortho C–H borylation of aniline derivatives using N -pivaloyl DGs and BBr 3 (Fig.…”