2219-53-6Relevant academic research and scientific papers
Copper-Mediated Dichotomic Borylation of Alkyne Carbonates: Stereoselective Access to (E)-1,2-Diborylated 1,3-Dienes versus Traceless Monoborylation Affording α-Hydroxyallenes
Guo, Kun,Kleij, Arjan W.
supporting information, p. 4901 - 4906 (2021/01/21)
A mild copper-mediated protocol has been developed for borylation of alkynyl cyclic carbonates. Depending on the nature of the borylating reaction partner, either stereoselective diborylation of the propargylic surrogate takes place, providing convenient access to (E)-1,2-borylated 1,3-dienes, or traceless monoborylation occurs, which leads to α-hydroxyallenes as the principal product. The dichotomy in this borylation protocol has been scrutinized by several control experiments, illustrating that a relatively small change in the diboron(4) reagent allows for competitive alcohol-assisted protodemetalation to forge an α-hydroxyallene product under ambient conditions.
Control of regioselectivity in Pd(0)-catalyzed coupling-cyclization reaction of 2-(2′,3′-allenyl)malonates with organic halides
Ma, Shengming,Jiao, Ning,Zhao, Shimin,Hou, Hairong
, p. 2837 - 2847 (2007/10/03)
The regioselectivity in the Pd(0)-catalyzed coupling-cyclization of 2-(2′,3′-allenyl)malonates with organic halides is determined by the steric and electronic effects of both substrates. By deliberate control of the reaction conditions, the regioselectivity of this reaction can be tuned. With conditions A and B, the reaction afforded vinylic cyclopropane derivatives, while with conditions C and D, the reaction afforded cyclopentene derivatives in a highly selective manner. Under similar conditions, 1-alkenyl halides tend to form more three-membered cyclic products. The increased steric hindrance at the 2′-positon of the allene moiety and aryl halides favors the formation of five-membered cyclic products. The regioselectivity of the reaction may be explained by the comparison of the relative stabilities of syn- and anti-type π-allyl palladium intermediates.
Efficient synthesis of 4-(2′-alkenyl)-2,5-dihydrofurans and 5,6-dihydro-2H-pyrans via the Pd-catalyzed cyclizative coupling reaction of 2,3- or 3,4-allenols with allylic halides
Ma, Shengming,Gao, Wenzhong
, p. 6104 - 6112 (2007/10/03)
In the absence of a base, palladium(II) catalysts, such as PdCl2, PdCl2(CH3CN)2, Pd(OAc)2, and [(π-C3H5)PdCl]2, can catalyze the cyclizative coupling reaction of 2,3- or 3,4-allenols with allylic halides in DMA at room temperature to provide 2,5-dihydrofurans and 5,6-dihydro-2H-pyrans, respectively, in moderate to good yields. Under similar reaction conditions, nonsubstituted 2,3-allenol 1s affords bimolecular cyclizative coupling product 5s as the major product. The scope of the reaction and its mechanism have been studied briefly. On the basis of the experimental results, the transformation was believed to proceed via a divalent palladium-catalyzed pathway.
