Silica gel promotes the lactonization and the concomitant aryl rearrangement of 4-aryl-5-tosyloxy pentanoates (3c-j) to give γ-lactones along with complete inversion in high yields.
Intramolecular Reaction of a Phenonium Ion. Novel Lactonization of 4-Aryl-5-tosyloxypentanoates and 4-Aryl-5-tosyloxyhexanoates Concomitant with a Phenyl Rearrangement<sup>1</sup>
of the aromatic ring on the reactivity, it was found that the reaction proceeded via a phenonium ion. This finding was supported by the stereochemical results for the lactonization of opticalactive 1. Silica gel-promoted lactonization of 1 gave only gamma-lactone 2, whereas that of 3 afforded gamma-lactone 4 and delta-lactone 5. These lactonizations proved to be kineticallycontrolled. On the other
Reaction of Methyl 4,5-Epoxy-(2E)-pentenoate with Arylcopper Reagents.
作者:Shinji NAGUMO、Shigeyuki IRIE、Hiroyuki AKITA
DOI:10.1248/cpb.44.675
日期:——
The reaction of methyl 4, 5-epoxy-(2E)-pentenoate (1) with various arylcopper reagents was studied. Basically, all arylcopper reagents react with 1 in SN2 fashion. However, addition of BF3 causes reversal of the regioselectivity, which can be rationalized in terms of a two-step conversion by way of methyl 4-bromo-5-hydroxy-2-pentenoate (5).