10.1016/j.tetlet.2016.11.084
The research presents a novel approach for selectively deprotecting aryl allyl ethers to yield phenols using copper boryl complexes. The purpose of this study is to develop an alternative to traditional palladium-based methods for deprotecting allyl ethers, which are commonly used as protecting groups for alcohols in organic synthesis. Lithium methoxide (LiOMe) plays a crucial role as a base in the copper-catalyzed deallylation process. Specifically, it is used in combination with copper(I) iodide (CuI), triphenylphosphine (PPh3), and bis(pinacolato)diboron (B2pin2) to facilitate the selective cleavage of aryl allyl ethers to yield the corresponding phenols. The study found that LiOMe is the most effective base among several tested, suggesting that it may be essential for the formation of a Bpin-OMe adduct, which is necessary for the reaction to proceed efficiently. This base helps in activating the copper boryl reagent system, enabling the mild and selective deprotection of aryl allyl ethers under the described conditions.
10.1039/C29690000220
The study investigates the photochemical synthesis of benzocyclopropenone (IVa) through the decomposition of lithium 3-p-tolyl sulphonylamino-1,2,3-benzotriazin-4(3H)-one (Ia) and its 6-chloro-analogue (Ib). The precursor compounds are prepared by diazotization of anthranilic acid toluene-sulfonohydrazides and subsequent treatment with lithium hydride or lithium methoxide. Upon UV excitation, Ia decomposes to yield lithium toluene-p-sulphonate, methyl benzoate, and o-methoxybenzoic acid toluene-p-sulphonohydrazide, while Ib gives lithium toluene-p-sulphonate, methyl p-chlorobenzoate, and 5-chloro-2-methoxy-benzoic acid toluene-p-sulphonohydrazide. The formation of p-chlorobenzoate suggests the involvement of a benzocyclopropenone intermediate (IVb) in the reaction mechanism, which undergoes hemiacetal formation and Favorskii ring-opening to produce the ester. The study also explores the thermolysis of Ia in triglyme, which yields triptycene, possibly via decarbonylation of IVa to form benzyne (VIIIa), and the photolysis of Ib in benzene, producing a small amount of p-chlorobenzophenone.
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