Reaction of salicylaldehydes (1) with carbethoxymethylenetriphenylphosphorane in diethylaniline under reflux gave coumarins (3) in moderate to high yield except 3-methoxycarbonylsalicyladehyde (1e) as summarized in Table I. The substituent effects are discussed. A substituent at C6 on 1 usually facilitated the formation of the coumarin ring regardless of its electronic character.
Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to Coumarins: Asymmetric Synthesis of (<i>R</i>)-Tolterodine
作者:Gang Chen、Norihito Tokunaga、Tamio Hayashi
DOI:10.1021/ol0507367
日期:2005.5.1
[reaction: see text]. Rhodium-catalyzedasymmetric1,4-addition of arylboronic acids to coumarins proceeded with high enantioselectivity in the presence of a rhodium catalyst (3 mol %) generated from Rh(acac)(C2H4)2 and (R)-Segphos to give the corresponding (R)-4-arylchroman-2-ones in over 99% ee. This asymmetric reaction was applied to the synthesis of (R)-tolterodine.
Lewis Base‐Catalyzed Cycloaddition of Heterocyclic Alkenes with 2,2,2‐Trifluorodiazoethane (CF
<sub>3</sub>
CHN
<sub>2</sub>
): Access to Trifluoromethylated Pyrazolines and Pyrazoles
作者:Tingting Cao、Zhen Yang、Yunfang Sun、Nannan Zhao、Shan Lu、Jing Zhang、Lei Wang
DOI:10.1002/ejoc.202100521
日期:2021.6.7
An efficient Lewis base catalytic protocol to biologically important trifluoromethylated pyrazolines and pyrazoles is developed through [3+2] triazene-heterocycilc alkene cycloaddition reactions of an array of oxa-/aza-benzonorbornadienes and coumarins with CF3CHN2. This approach features good functional group tolerance and scaffold diversity. Synthetic utility of the protocol is highlighted by late-stage
Straightforward Assembly of Benzoxepines by Means of a Rhodium(III)-Catalyzed C–H Functionalization of <i>o</i>-Vinylphenols
作者:Andrés Seoane、Noelia Casanova、Noelia Quiñones、José L. Mascareñas、Moisés Gulías
DOI:10.1021/ja410538w
日期:2014.1.22
Readily available o-vinylphenols undergo a formal (5 + 2) cycloaddition to alkynes when treated with catalytic amounts of [Cp*RhCl2](2) and Cu(OAc)(2). The reaction, which involves the cleavage of the terminal C-H bond of the alkenyl moiety, generates highly valuable benzoxepine skeletons in a practical, versatile, and atom-economical manner. Using carbon monoxide instead of an alkyne as reaction partner leads to coumarin products which formally result from a (5 + 1) cycloaddition.
REDUCTIONS WITH NICKEL-ALUMINUM ALLOY AND AQUEOUS ALKALI. PART VIII. HYDROGENOLYSIS OF FURAN DERIVATIVES<sup>1</sup>