The thermal reaction of dirhodium tetraacetate with tris(3-thienyl) phosphine (3TP), diphenyl(3-thienyl)phosphine (3TPPh(2)), and diphenyl(2-thienyl) phosphine (2TPPh(2)) gives rise to mono-cyclometalated and bis- cyclometalated compounds; the latter can have a head-to-head (H-H) or head-to-tail (H-T) configuration. Bis-cyclometalated compounds with H-T configuration can be prepared in high yield under photochemical conditions or by combining irradiation with subsequent thermal treatment in acetic acid. The reactivity order of aromatic ring C-H activation is phenyl < 2-thienyl << 3-thienyl, which leads to a selective activation of the thienyl ring. Thus, only one mono-cyclometalated compound is obtained from the thermal reaction with 3TPPh(2), and activation of the thienyl ring competes favorably with activation at the phenyl rings in the case of 2TPPh(2). The reaction of these mono-cyclometalated compounds with d(4)-acetic acid was monitored by H-1 NMR spectroscopy, which demonstrates that the H/D exchange occurs during the demetalation step. The energy values calculated (DFT) for the different compounds agree with the experimental results.
Photochemical Synthesis of Phosphinolines from Phosphonium−Iodonium Ylides
作者:Elena D. Matveeva、Tatyana A. Podrugina、Marina A. Taranova、Anatolyi A. Borisenko、Andrey V. Mironov、Rolf Gleiter、Nikolay S. Zefirov
DOI:10.1021/jo101993a
日期:2011.1.21
phosphinolines prevails. A second series of experiments was carried out with mixed ylides in which one phenyl ring at the triarylphosphonium group was replaced by a thienyl group. In this case, we observe only an intramolecular reaction with the thienyl ring to yield the phosphinolines 21−23. In a third test, we replaced in the mixed ylides 1a, 1b the COR group by a CN substituent. This modification leads to phosphinolines