Fries Rearrangement of Aryl Formates: A Mechanistic Study by Means of 1H, 2H, and 11B NMR Spectroscopy and DFT Calculations
摘要:
H-1, H-2, and B-11 NMR spectroscopy has been used to study the mechanism of the Fries rearrangement of aryl formates promoted by boron trichloride by monitoring both the substrate and the Lewis acid. DFT calculations were employed to investigate the energetics of several reaction paths and to calculate NMR chemical shifts of key intermediates and products. After the formation of a 1:1 substrate-Lewis acid adduct, the rearrangement proceeds in two steps, beginning with the cleavage of the ester bond and the release of formyl chloride in situ, which, in turn, acts as a formylating agent, introducing an aldehydic functionality into the aromatic ring. The high regioselectivity (only the ortho product is obtained) is also accounted for by the proposed intermolecular, Lewis acid-assisted mechanism.
same as those resulting from the Friesrearrangement of 3-methoxy- and 3,5-dimethoxy-phenyl formate. These results represent a novel regioselective synthetic route to aromatic aldehydes, using phenyl formate as a source of formylating agent. They also unambiguously prove that the Friesrearrangement of aryl formates (that we recently investigated in J. Org. Chem. 71, 9331–9340, 2006) is intermolecular:
BBr<sub>3</sub>-Assisted Preparation of Aromatic Alkyl Bromides from Lignin and Lignin Model Compounds
作者:Xuan Li、Jianghua He、Yuetao Zhang
DOI:10.1021/acs.joc.8b01628
日期:2018.9.21
important organic synthesis reagents, aromatic alkylbromides, in high to excellent yields (up to 98%). Preliminary studies also highlight the prospect of this method for the effective cleavage of different types of C–O bonds in real lignin. A total 14 wt % yield of aromatic alkylbromide, 4-(1,2-dibromo-3-hydroxypropyl)benzene-1,2-diol (10), has been obtained from an extracted lignin through this method
Preparation and properties of methoxytrifluorosilane, and study of its reactions with boron trihalides
作者:W. Airey、G.M. Sheldrick
DOI:10.1016/0022-1902(70)80588-7
日期:1970.6
MeOSiF3 is formed when gaseous MeOSiCl3 is passed through SbF3; its reaction with BBr3 provides a convenient preparation of F3SiBr. Similarly BF3 and BCl3 yield SiF4 and F3SiCl respectively. The other product in these reactions is MeOBX2 (X = Br, F, Cl respectively), but the methoxy boron dibromide decomposes to give methyl bromide and boron oxybromides.