Solid phase synthesis of 2-acyl-3,7,8-substituted-5-oxo-2-azabicyclo[2.2.2]octane and triaza analogs: Resin Activation/Capture Approach/REACAP Technology
摘要:
The resin-bound enol ether scaffold generated using the Resin Activation/Capture Approach (REACAP) Technology was further elaborated via a stereospecific Diels-Alder addition to afford a series of highly rigid substituted 5-oxo-2-azabicyclo[2.2.2]octane and triaza analogs. (C) 1999 Elsevier Science Ltd. All rights reserved.
The photodissociation spectroscopy of MgCH+4 has been studied in a reflectron time-of-flight mass spectrometer. MgCH+4 molecular absorption bands are observed to the red of the Mg+(3 2PJ←3 2S1/2) atomic ion resonance lines. The photofragmentation action spectrum consists of a broad structureless continuum ranging from 310 nm to 342 nm, and peaking near 325 nm. In this spectral region, both the nonreactive (Mg+), and two reactive fragmentation products (MgH+ and MgCH+3) are observed, all with similar action spectra. The product branching is independent of wavelength, Mg+:MgCH+3:MgH+∼60:33:7. The absorption is assigned to the transition (1 2E←1 2A1) in C3v symmetry (with η3 coordination), followed by a geometrical relaxation of the complex toward states of 2B1 and 2B2 symmetry in C2v geometry (with η2 coordination). Dissociation requires a nonadiabatic transition to the ground electronic surface. Analysis of broadening in the photofragment flight time profile shows the nonreactive Mg+ product angular distribution to be isotropic, with an average translational energy release which increases slightly from Et∼370±150 cm−1 at 332.5 nm to Et∼520±180 cm−1 at 315 nm. These values are less than 2% of the available energy and are well below statistical expectations. Analogous experiments on MgCD+4 show the kinetic energy release in the nonreactive channel to be significantly larger for the CD4 case, ranging from Et∼540±180 cm−1 at 332.5 nm to Et∼830±200 cm−1. These results clearly demonstrate that the dissociation is nonstatistical. Preliminary ab initio potential surface calculations suggest a possible dynamical mechanism to explain these unusual results.