Lewis acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with 2-naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene-fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel-Crafts-type addition of 2-naphthols to cyclopropanes takes place, thus affording functionalized 2-naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields.
Although nucleophilic phosphine-catalysis is a powerful tool for the construction of various carbocycles and heterocycles, the reactions in which phosphines are incorporated into the final product are rare, and the reports on phosphine addition to highly electrophilic arynes are scarce. Herein, we report the phosphine triggered multicomponent reaction of arynes and aldehydes, which takes place via the formal [3+2] cycloaddition of an initially generated 1,3-phosphonium zwitterion from phosphines and arynes with aldehydes. The reaction resulted in the formation of a diverse range of stable pentacovalent phosphoranes in good yields based on the benzooxaphosphole system.
Employing a bifunctional
catalyst based on a copper(I)/NHC complex
and a guanidine organocatalyst, catalytic ester reductions to alcohols
with H2 as terminal reducing agent are facilitated. The
approach taken here enables the simultaneous activation of esters
through hydrogen bonding and formation of nucleophilic copper(I) hydrides
from H2, resulting in a catalytic hydride transfer to esters.
The reduction step is further facilitated by a proton shuttle mediated
by the guanidinium subunit. This bifunctional approach to ester reductions
for the first time shifts the reactivity of generally considered “soft”
copper(I) hydrides to previously unreactive “hard” ester
electrophiles and paves the way for a replacement of stoichiometric
reducing agents by a catalyst and H2.
The highly monoselective N-arylation of aromatic tertiary amines using a transition-metal-free approach using arynes has been developed. The reaction afforded functionalized diaryl amines in moderate to excellent yield. High levels of functional group compatibility especially with halogen containing substrates, dyes and donor-acceptor systems, and high yields of products are the notable features of the present reaction.
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