The rule of infrared spectroscopic characteristics of the five alpha, alpha'-dioxoketene cyclic s, s-acetals was studied, and the influence of the molecular structure on the IR was indicated. All 1H and 13C NMR chemical shifts of the five compounds were assigned, and the effects of structures on the chemical shifts of 1H and 13C NMR were discussed. The rule of change is the same as that of IR. The study offers a method of elicitation for studies on the structure and the spectroscopy of this kind of compounds.
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Indanedioneketene, a compound resulting from the thermal degradation of the phenyliodonium ylide of lawsone, dimerizes quantitatively to a spiro-oxetanone derivative, a key compound for further transformations. A theoretical electronic structure study of this unusual for alpha-oxoketenes [2 + 2] cyclization reaction both in the gas phase (DFT, MP2) and in dichloromethane solution (DFT), provides support for (a) a single-step, transition-state (involving a four-membered cyclic ring) charge-controlled, concerted mechanism and (b) a [4 + 2] cyclization reaction, not observed but studied theoretically in this study. A parallel study of an open-chain alpha,alpha'-dioxoketene dimerization explains the difference in the stability and reactivity observed experimentally between the cyclic and open-chain products.
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Laboratory of Organic Chemistry, Department of Chemistry, University of Thessaloniki, Greece.
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Guang Pu Xue Yu Guang Pu Fen Xi
February 1998
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian.
In this paper, the ultraviolet spectra of alpha,alpha'-dioxoketene cyclic S,S-acetals (N,N-acetals) have been studied and their changing characters with the change of chemical structure have been indicated.
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