Cleavage of C(aryl)−CH₃ Bonds in the Absence of Directing Groups under Transition Metal Free Conditions

Abstract

Organic chemists now can construct carbon–carbon σ‐bonds selectively and sequentially, whereas methods for the selective cleavage of carbon–carbon σ‐bonds, especially for unreactive hydrocarbons, remain limited. Activation by ring strain, directing groups, or in the presence of a carbonyl or a cyano group is usually required. In this work, by using a sequential strategy site‐selective cleavage and borylation of C(aryl)−CH3 bonds has been developed under directing group free and transition metal free conditions. Methyl groups of various arenes are selectively cleaved and replaced by boryl groups. Mechanistic analysis suggests that it proceeds by a sequential intermolecular oxidation and coupling of a transient aryl radical, generated by radical decarboxylation, involving a pyridine‐stabilized persistent boryl radical.

tert‐Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis

“…The reaction proceeds via the addition of TBN to CCb ond followed by a sequence of hydration,i somerization and aromatic C(sp 2 )ÀH oxidation (Scheme 44). [70] In this product water is the origin of two oxygen atoms which was confirmed by 18…”

“…Diborylation product can be obtained by the sequential run of standard condition albeit in a low yield of 31 %. Based on the preliminary mechanistic study it was confirmed that the reaction continues via a sequential radical demethylative C−C bond cleavage followed by borylation (Scheme ) …”

“…Based on the preliminary mechanistic study it was confirmed that the reaction continues via asequential radical demethylative CÀCb ond cleavage followed by borylation (Scheme 9). [18] Based on the literature precedents and controle xperiments ap lausible mechanism was proposed. The demethylative borylation reaction proceeds via sequential radical demethylation followed by borylation.…”

Organic Borylation Reactions via Radical Mechanism

“…2019 年, 康彦彪课题组报道了加热条件下促进的 芳基羧酸 NHPI 酯的脱羧硼酯化反应(图 10) [30] . 该反应 以芳基甲基型化合物作为起始底物, 亚硝酸叔丁酯作为 氧化剂, 可以原位产生芳基羧酸 NHPI 酯, 随后在加热 图 9 芳基羧酸衍生物的脱羧硼酯化反应 Scheme 9 Decarboxylative borylation of aryl carboxylic acid derivatives 图 10 经由芳基羧酸 NHPI 酯的 C(aryl)-CH 3 硼酯化反应 Scheme 10 Borylation of C(aryl)-CH 3 bond via N-hydroxyphthalimide ester 条件下经吡啶衍生物的活化, 实现自由基过程的硼酯化 反应.…”

Transition‐Metal‐Free Deconstructive Lactamization of Piperidines

“…[5] Fortunately,aconsiderable number of remarkable transition-metal-free synthetic protocols are reported daily. [6][7][8][9][10] In recent years,o ur research group has developed efficient, accessible,e conomic,a nd environmentally friendly protocols for the functionalization of simple N-heterocycle substrates to give relevant bioactive precursors. [11] Thesuccess of this direct functionalization of pre-existing N-heterocycles lies in the highly selective CÀHo xidation at the a position mediated by cheap and environmentally friendly reagents such as NaClO 2 ,N aOCl, and 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO), in which, under modulated conditions,t he C À Hoxidation at the b position can be achieved, even under catalytic conditions.…”