A new entry of highly nucleophilic CHBr3–TiCl4–Mg system for the stereoselective synthesis of 1-alkenyl bromides

Pd-Catalyzed Regio- and Stereoselective Addition of Boronic Acids to Silylacetylenes: A Stereodivergent Assembly of β,β-Disubstituted Alkenylsilanes and Alkenyl Halides

“…On the other hand, stereodefined β,β-disubstituted alkenyl halides are versatile building blocks in organic synthesis that can act as convenient precursors for the preparation of stereodefined trisubstituted alkenes via transition-metal-catalyzed cross-coupling reactions. However, there are only a limited number of methods for the regio- and stereoselective construction of these motifs . With the current boron addition reaction in hand, we decided to explore a mild as well as efficient protocol for the synthesis of β,β-disubstituted alkenyl halides.…”

“…It constitutes the first regio- and stereoselective hydroarylation or hydroalkenylation of aryl and alkenyl silylacetylenes with boronic acids. Meanwhile, an operationally simple and stereodivergent method for the assembly of β,β-disubstituted ( Z )- and ( E )-alkenyl halides via a sequential boron addition/ N -halosuccinimide-mediated halodesilylation reaction has been developed, thus providing a stereodivergent and expeditous approach to stereodefined trisubstituted ( Z )- and ( E )-alkenes by the cross-coupling strategy.…”

Chromium-catalyzed olefination of arylaldehydes with haloforms assisted by 2,3,5,6-tetramethyl-N,N′-bis(trimethylsilyl)-1,4-dihydropyrazine

“…1(a)). 5 Takai et al further explored carbonyl olefination with wide functional group tolerance using chromium( ii ) dihalide. In fact, excess amounts of CrCl 2 -mediated olefination of carbonyl compounds with geminal dihalides, 6 while the catalytic variant was demonstrated using CHI 3 , Me 3 SiCHX 2 (X = Br, I), and (pin)BCHCl 2 in combination with excess amounts of metal reductants, such as zinc or manganese powders (Fig.…”

Bromoform Activation. TiCl4–Mg-Promoted CHBr2– and CBr3– Transfer to a Variety of Aldehydes and Ketones

“…Can the dibromomethyltitanium and tribromomethyltitanium reagents be generated directly via oxidative addition of the C–Br bond to TiCl 4 –Mg bimetallics? Earlier work in our laboratories established the feasibility of CH n X m –TiCl 4 –Mg system as highly nucleophilic methylene and halomethylene carbenoids to effect carbonyl-olefination . In searching for new strategies based upon the concept of simple oxidative addition, we turned our attention to the concept of a polyhalomethyltitanium synthesis based upon a titanium–magnesium bimetallic-mediated oxidative addition of the halides.…”