Table 3.
Scope of Selective N-Demethylation and Late-Stage Applicationsa
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Reactions were performed with 0.2 mmol of substrate at ambient temperature in MeCN (0.1 M) using 1 mol% PC (5CzBN), NiCl2(H2O)6 (5 mol%), dtbbpy (8 mol%), Br2 (1.5 equiv), NaOPiv (1 equiv) and H2O (36 μL) under 12-30 h of blue LED light irradiation (427 nm), followed by adding NEt3 (2 equiv) and Boc2O (1 equiv). Yields refer to isolated products after purification by flash chromatography. Regioselectivities were determined by isolated yield.
Troc-Cl (1 equiv) was used in place of Boc2O.
TRIP-Br Br3 (1.1 equiv) and Ni(cod)2 was used in place of Br2 and NiCl2(H2O)6 for improved site selectivity.
The ratios in parentheses refer to site selectivity between the methyl position and position(s) highlighted in grey determined by crude 1H NMR.