N-Bromosuccinimide as a Regioselective Nuclear Monobrominating Reagent for Phenols and Naphthols

Amine‐Catalyzed Highly Regioselective and Stereoselective C(sp2)–C(sp2) Cross‐Coupling of Naphthols with trans‐α,β‐Unsaturated Aldehydes

“…To our delight, not only was the desired product 3 a obtained, but also good yields and high stereoselectivities ( E/Z ) were achieved (Table , entries 1–4). The results indicated that the bromination reaction occurred at the para ‐position of 1‐naphthanol in CH 3 CN . The in situ formation procedure can improve the efficiency of the two‐step organic transformations minimizing the undesired F–C cyclization cascade reaction.…”

“…As tudy by CarreÇo et al revealed that the regioselectivity could be controlled by reactionm edia. [16] When the process was conducted in CH 3 CN using N-bromosuccinimide (NBS) as the brominationr eagent, the para-bomination occurred dominantly.…”

“…The resultsi ndicated that the bromination reaction occurreda tt he para-position of 1naphthanol in CH 3 CN. [16] The in situ formation procedure can improvet he efficiency of the two-step organic transformations minimizing the undesired F-C cyclization cascade reaction. It is reasonably speculated that the in situ para-bromination involved an arenium ion followed by base-assisted deprotonation (rearomatization), and this generates more nucleophilic para-carbon for the subsequent Friedel-Crafts (e.g.,M ichael reaction) with trans-cinnamaldehyde (2a).…”

“…The outcomef rom the investigation suggested that the process conducted in CH 3 CN was the moste fficient presumably owing to the betters olubility for 1a and betterc ontrol of regioselectivity. [16] Finally, the base additives were critical for the process, as results of facilitating the bromination, activation of the phenol moietyb yd eprotonation, assisting the ring opening of cyclopropylr ing (see Scheme 3, proposed catalytic cycle) andt he neutralization of the produced HBra nd NaOAc (5.0 equiv) was the choice.…”

Epigenetic profiling of the antitumor natural product psammaplin A and its analogues

“…57 As shown on Scheme 1, the amino group of L-tyrosine 2 was oxidized to the hydroxyimino ester 3 in 60% yield using Na 2 WO 4 and H 2 O 2 in ethanol. 58 A monobrominated product 4 was obtained by treatment of 3 with one equivalent of NBS in CH 3 CN at 25°C, 58,59 with no evidence of formation of the dibromo derivative or the dibrominated spirocyclic isoxazoline. 57 After saponification of 4 the carboxylic acid 5 was coupled with cystamine using Hoshino's conditions.…”