anti‐Selective Borylstannylation of Alkynes with (o‐Phenylenediaminato)borylstannanes by a Radical Mechanism

Abstract

We have achieved the first anti‐borylstannylation of alkynes by using (o‐phenylenediaminato)borylstannanes. This reaction afforded 1‐boryl‐2‐stannylalkenes with excellent regio‐ and stereoselectivity by a radical mechanism. This anti‐addition manner is in sharp contrast to the syn‐selectivity obtained during transition metal‐catalyzed borylstannylation. The mild radical conditions enabled a broad substrate scope, and various types of aromatic and aliphatic alkynes were applicable. The origin of regio‐ and stereoselectivity was elucidated by DFT calculation of the reaction mechanism. The application of the borylstannylation products to cross‐ or homocoupling reactions provided ready access to either triarylethenes or bisborylbutadienes.

Radical-mediated carboselenation of terminal alkynes under mild conditions

“…Subsequently, the anti-Markovnikov addition of the radical I to alkyne 1 afforded the vinyl radical II [eqn (2)]. 24 Finally, the vinyl radical II was trapped by diorganyl diselenide 3 from more favorably the sterically less hindered side to give ( E )-γ-seleno-substituted allyl nitrile 4 [eqn (3)]. 15…”

Facile and General Electrochemical Diselenylation of Terminal Alkynes

“…Alkynes are one of the most flexible building blocks and widely used as sustainable feedstocks for chemical synthesis, as well as in the production of numerous medications and materials. , Catalytic difunctionalization of these π systems is a direct and efficient method to access a variety of structurally diverse trisubstituted compounds. − Trisubstituted alkenes are pivotal structural motifs in the structure of numerous medicines − and materials, as well as helpful precursors for other functional groups and chiral centers . The methods employed, however, rely heavily on the use of organometallic species and require high-temperature or multistep reactions (Scheme a). − More recently, radical-mediated reactions have been devised, which provide an effective technique for difunctionalizing terminal alkynes. − In general, a radical is generated from various radical precursors, such as sulfonyl chlorides, α,β-unsaturated ketones, activated alkyl bromides, fluoroalkyl iodides, etc., − which is via a single electron transfer (SET) process employing transition metal species, − photocatalysts, − or electrocatalysis (Scheme b). These processes are usually transition metal-catalyzed multicomponent reactions, and heavy metal residues are long-standing issues.…”

Metal-Free One-Pot Multi-Functionalization of Unsaturated Compounds with Interelement Compounds by Radical Process

“…The authors estimated that the vacant p -orbital of the boron in ( o -phenylenediaminato)borylstannane conjugated with the orbital of the phenylenediamine structure, and the efficient delocalization lowered the energy level of the LUMO; this allowed a large interaction with the SOMO of the alkyl radical (from initiators), and the radical borylation and stannylation took place smoothly. In addition, the S H 2 reaction with generated vinyl radicals and ( o -phenylenediaminato)borylstannane proceeded in a manner that avoided steric repulsion, and the corresponding products were obtained with anti -selectively ( Scheme 21 ) [ 116 , 117 ].…”