Access to 1,1‐Diborylalkenes and Concomitant Stereoselective Reactivity

Abstract

Gem‐diborylalkenes have emerged as efficient reagents for selective cross‐coupling reactions, reduction approaches and Michael additions. The synthesis of 1,1‐diborylalkenes involves condensation of polyborated compounds with aldehydes or ketones followed by B–O elimination, geminal diboration of 1,1‐dihaloalkenes, 1‐haloalkenes or terminal alkynes, dehydrogenative borylation of alkenes, borylation of alkynylboronates and hydroboration of alkynylboronates. These new sets of reactions are general for a wide range of substrates and they can be understood to have complementary mechanisms.

Stereoselective Diels–Alder Reactions of gem-Diborylalkenes: Toward the Synthesis of gem-Diboron-Based Polymers

“… 11 , 20 For example, gem -diborylalkenes 2 have served as building blocks for Suzuki–Miyaura cross-coupling, nucleophilic partners, reduction approaches, Michael additions, 21 radical chemistry, 22 and other reactions. 13 , 23 …”

“…Among polyboron-containing structural motifs, (unsymmetrical) gem- diboron derivatives ( 2 , 3′ ) are a well-known emerging class with good potential for novel synthetic applications (Figure A). − The special properties and structures of bisnucleophile gem -diboryl compounds 2 and 3′ (termed geminated organodimetallics) , have attracted increasing attention from synthetic chemists, particularly in constructing C–C/C–heteroatom bonds. In recent years, gem -diboryl compounds 2 and 3′ have been widely adopted as coupling partners in synthetic chemistry. , For example, gem -diborylalkenes 2 have served as building blocks for Suzuki–Miyaura cross-coupling, nucleophilic partners, reduction approaches, Michael additions, radical chemistry, and other reactions. , …”

Organosuperbase Catalyzed 1,1-Diboration of Alkynes

“…6,7 Diborylalkenes are probably the most utilized synthetic precursors in this sub-class, as they offer distinctive pathways to the construction of multi-substituted alkenes in regio-or stereoselective manner. 8,9 Diborylalkenes in turn are typically produced by diboration of alkynes via addition reactions. However, the nature of these addition reactions often leads to 1,2-diborylalkenes being formed as the products.…”

“…However, the nature of these addition reactions often leads to 1,2-diborylalkenes being formed as the products. 2,3,7,8,[10][11][12] Methods to synthesize the 1,1-diborylalkene counterparts have only been reported more frequently in the recent years. 8 Most of them [13][14][15][16] involved transition metals catalysts such as [Co], 17 [Zn], 18 [Cu], 19 [Pd] 20 or [Ir] 21 to facilitate diboration of non-activated terminal alkynes (Scheme 1, top).…”

“…2,3,7,8,[10][11][12] Methods to synthesize the 1,1-diborylalkene counterparts have only been reported more frequently in the recent years. 8 Most of them [13][14][15][16] involved transition metals catalysts such as [Co], 17 [Zn], 18 [Cu], 19 [Pd] 20 or [Ir] 21 to facilitate diboration of non-activated terminal alkynes (Scheme 1, top). The diboration of activated terminal alkynes bearing electron-withdrawing substituents is relatively easier and can be promoted with alkali-metal bases as catalysts.…”