Synthesis of Cyclopentadienes for Cyclopentadienyl Ligands via Cp*Rh<sup>III</sup>-Catalyzed Formal sp<sup>3</sup> C–H Activation/Spiroannulations
作者:Yongzhuang Wang、Xiaoli Huang、Qin Wang、Yuhai Tang、Silong Xu、Yang Li
DOI:10.1021/acs.orglett.0c03982
日期:2021.2.5
An efficient Cp*RhIII-catalyzed formal C(sp3)–H activation/spiroannulation of alkylidene Meldrum’s acids with alkynes has been developed using catalytical Cu(OAc)2 and air as the oxidant. This reaction demonstrates a new and straightforward approach to spirocyclopentadienes with Meldrum’s acid moieties in good to excellent yields under mild reaction conditions with a broad substrate scope. Notably
The infraredspectra of isopropylidene malonate and some of its derivatives have been examined and compared with those of open-chain malonate esters and of 5,5-dimethylcyclohexane-1,3-dione. Two bands in the carbonyl stretching region are attributed to vibrational coupling of the carbonyl groups in the cyclic esters. There is no evidence that isopropylidene malonate exists in the enolic form either
Photochemistry of Deuterated Acetylketenes: Matrix Isolation Infrared Spectroscopic and ab Initio Studies
作者:Ralf H. Zuhse、Ming Wah Wong、Curt Wentrup
DOI:10.1021/jp9529026
日期:1996.1.1
The partially deuterated s-Z and s-E conformers of acetylketene (1 and 2) were generated by flash vacuum pyrolysis of two different deuterated precursors, 3 and 4. The conformer mixture was characterized by low-temperature FTIR spectroscopy in Ar, N-2, and Xe matrices. The observed frequencies and intensities are in excellent agreement with ab initio calculations at the MP2/6-31G* and B-LYP/6-31G* levels. Irradiation of Ar matrices in the UV (313 nm) caused the appearance of new sets of absorptions, which disappeared upon annealing of the matrices to 35 K. Difference spectra revealed no new absorptions due to OD bands arising from photoisomers 7-10, thereby rigorously proving that no C-D/O-D tautomerism takes place and that the new absorptions observed are due to exceptionally prominent photochemically populated matrix sites.