Copper(II)-catalyzed silylation of substituted alkynylcarbonyl chemical substances was investigated. Considering that

Copper(II)-catalyzed silylation of substituted alkynylcarbonyl chemical substances was investigated. Considering that a gentle method with wide substrate scope practical group tolerance and high stereoselectivity happens to be missing and our fascination WZ4002 with Cu-catalyzed boryl[10] and silyl[11] conjugate addition [12] we wanted to develop a procedure to handle these shortcomings. Specifically we utilize commercially obtainable Me2PhSiBpin [13] as the silicon resource which was lately utilized by Loh and co-workers in the formation H3.5 of linear and branched vinylsilanes.[14] Herein we record a copper(II)-catalyzed conjugate addition of substituted alkynyl carbonyls to create the related β-silylated products. Remarkably the technique furnishes a substrate-controlled diastereodivergent usage of stereoisomeric items: aldehydes selectively afford olefins whereas esters and amides specifically generate the contrary alkene geometry. The process offers several useful advantages. First of all WZ4002 it utilizes a catalytic quantity of redox steady and inexpensive changeover metal-a copper(II) source-that can be resistant to oxidation. Copper(I) resources require special managing which includes either Schlenck methods or usage of a glovebox. Subsequently WZ4002 the reaction is insensitive to provides and moisture a green chemistry process that utilizes water mainly because the solvent. Finally the technique is gentle being performed available to the atmosphere at rt within 2-4 h. We initiated our investigations by analyzing the appropriate foundation additive that may activate a B-Si relationship (Desk 1). We previously proven that 4-picoline was sufficiently effective in performing like a Bronsted foundation to activate a nucleophilic drinking water molecule towards Me2PhSiBpin and chemoselectively transfer silicon to α β-unsaturated carbonyl substances in the current presence of catalytic levels of copper (II).[11] A significant facet of our research may be the generation of the water steady nucleophilic Cu-Si intermediate to start silyl transfer towards the β carbon. A display of bases verified that a lot of organic and inorganic bases effectively catalyzed the transformation of 2-octyn-1-al (1b) to (percentage. Remarkably the geometry from the dual bond observed can be unlike that of a copper(I)-catalyzed addition to acetylenic esters lately reported by Molander.[15] The increase bond geometry was unambiguously designated by nuclear Overhauser impact (nOe) tests (start to see the Assisting Information for points). Furthermore exclusive development of β-silylated item was noticed. Control experiments recommend both amine and copper had been necessary for this a reaction to continue (entries 8-9). Finally investigations on copper reagents reveal several copper (II) resources effectively afford (selectivity (admittance 1). As the aldehyde beginning material had not WZ4002 been completely consumed in the response the equivalency of Me2PhSiBpin was risen to 1.5 in subsequent reactions. Therefore alkynyl aldehydes with alkyl substituents for the β-carbon which range from a brief pentyl to a a lot longer WZ4002 dodecyl string were efficiently changed to the related vinyl fabric silanes (2b-2e) in superb produce (up to 98%) and in up to 5:95 selectivity (entries 2-5). A far more sterically encumbered cyclohexyl group was also a competent substrate (admittance 6) but a phenyl substituent experienced from a contending 1 2 to cover 2g in 51% produce (admittance7).[16] To explore functional group tolerance from the reaction conditions propargyl amine 1h was changed into the required product in almost full selectivity (entry 8). Additionally α β γ δ-unsaturated ynal 1i particularly reacted for the β-carbon to cover 2i in 84% produce despite feasible completing δ- and 1 2 (admittance 9). Finally cyclopropylacrylaldehyde effectively underwent the response in excellent produce and selectivity affording the β-silylated item 2j (admittance 10). Desk 2 Silyl Conjugate Addition to Substituted Acetylenic Aldehydesa With a competent method for being able to access (items in moderate to great produces (entries 14-15). Desk 3 Silyl Conjugate Addition to Substituted Acetylenic Estersa WZ4002 We had been intrigued from the modification in stereochemical result from the reaction predicated on the identification from the carbonyl. An integral difference between these substrates can be.