67648-05-9Relevant articles and documents
Copper(I)-catalyzed regio- and stereoselective intramolecular alkylboration of propargyl ethers and amines
Iwamoto, Hiroaki,Ozawa, Yu,Kubota, Koji,Ito, Hajime
, p. 10563 - 10573 (2018/05/31)
The copper(I)-catalyzed regio- and stereoselective intramolecular alkylation of propargyl ethers and amines bearing an alkyl electrophilic moiety has been developed. The reaction showed high functional group tolerance and gave highly functionalized alkenylboronates bearing heterocyclic rings, which are versatile synthetic intermediates in organic chemistry. The borylation products can be transformed into multisubstituted alkenes through stereospecific transformations. Mechanistic studies showed that the chemo- and stereoselectivity of copper(I)-catalyzed borylation depends on the type of leaving group. Density functional theory calculations suggested that the regioselectivity of the borylcupration of the alkyne is controlled by the electronic effect of the oxygen atom of the propargyl ether in combination with the steric congestion between the boryl group and the substituent at the propargylic position.
Two Enabling Strategies for the Stereoselective Conversion of Internal Alkynes into Trisubstituted Alkenes
Huwyler, Nikolas,Radkowski, Karin,Rummelt, Stephan M.,Fürstner, Alois
supporting information, p. 12412 - 12419 (2017/09/06)
An expedient method for the C-methylation of alkenylstannanes with formation of trisubstituted alkenes is described, which relies on the use of MeI in combination with copper thiophene-2-carboxylate (CuTC) as promotor and tetra-n-butylammonium diphenylphosphinate as an effective tin scavenger; in some cases, it proved beneficial to further supplement the mixture with catalytic amounts of Pd(PPh3)4. Under these conditions, the reaction is robust, high yielding, and compatible with many functional groups that might not subsist under more traditional conditions used to C-alkylate organotin derivatives. A qualitative analysis of the reaction profile suggested that the in situ formation of a reactive organocopper intermediate and its interception by MeI is only barely faster than O-methylation of the phosphinate additive by the same alkylating agent. To guarantee high yields and prevent net protodestannation from occurring, the reaction protocol had to be optimized such that these competing processes are properly decoupled. The new method is particularly well suited for the stereoselective preparation of the (E)-2-methylbut-2-en-1-ol motif that is present in numerous natural products. Alternatively, this particular target structure can be accessed starting from α-hydroxy alkenylsiloxane precursors, which get C-methylated upon exposure to CuI/LiOtBu and MeI by what is thought to be a Brook rearrangement/ alkylation sequence. The required substrates are best prepared by ruthenium-catalyzed trans-hydrosilylation or trans-hydrostannation of propargyl alcohols.
Fluorine Effects on Group Migration via a Rhodium(V) Nitrenoid Intermediate
Wang, Cheng-Qiang,Zhang, Yu,Feng, Chao
supporting information, p. 14918 - 14922 (2017/10/12)
An unprecedented rhodium(III)-catalyzed hydroarylation of α,α-difluoromethylene alkynes with N-pivaloxyl aroylamides through sequential C?H activation and aryl migration is detailed herein. A large array of α,α-difluoromethylene alkynes and N-pivaloxyl aryl amides were amenable to this transformation, thus providing a novel synthetic protocol for the construction of difluorinated 2-alkenyl aniline derivatives in high yields and with excellent regioselectivity. Notably, unique fluorine effects were found to underlie the thus unconventional reaction manifold.
