Alkynylsilanes – a missing piece of different silylation agents, can serve as valuable substrates in the O‐silylation through a dealkynative coupling with alcohols or silanols. The described approach displays a whole array of advantages in terms of green chemistry and is a promising alternative to existing methodologies.
Stereoselective Synthesis of Pyrans from Epoxyalkenes: Dual Catalysis with Palladium and Brønsted Acid
作者:Noah A. Setterholm、Frank E. McDonald
DOI:10.1021/acs.joc.8b00026
日期:2018.6.15
We describe regio- and stereoselective cycloisomerizations of alcohols tethered to epoxyalkenes, to construct alkene-substituted pyrans. These transformations are best catalyzed by Pd(PPh3)4 in the presence of phosphite ligands, and with diphenylphosphinic acid as an essential Brønsted acid cocatalyst for activation of the epoxyalkene.
In nearly every total synthesis, silylating agents are employed in synthetic steps to protect sensitive functional groups. A Pt‐catalyzed hydrosilylation of various unsaturated substrates to prepare novel symmetrical and unsymmetrical disilazanes is described. The developed synthetic methodology is widely applicable and tolerates all manner of functional groups (e.g., amines, ethers, esters, halogens
OSitBuMe₂ and OSiiPr₃ groups, other than the OSiMe₃ group, were successfully substituted. The substitution reaction of enantiopure secondary benzylic silyl ether yielded the corresponding racemic thioether product, which suggested that the reaction of tertiary alkyl, secondary alkyl, benzylic, and propargylic silyl ethers would proceed via a SN1 mechanism.
Thermal Switchability of N-Chelating Hoveyda-type Catalyst Containing a Secondary Amine Ligand
作者:Karolina Żukowska、Anna Szadkowska、Aleksandra E. Pazio、Krzysztof Woźniak、Karol Grela
DOI:10.1021/om2011062
日期:2012.1.9
An investigation of aza analogues of the popular Hoveyda–Grubbs catalystcontaining a secondaryamineligand is presented, proving the crucial impact of steric as well as electronic factors on the catalyst’s stability and performance. The issue of latency in the reactivity profile of studied catalysts is examined, followed by structural and application studies.