Fully elaborated carbon

Having outlined a justification for the proposals of carbon tetrava-lence and self-linking, Couper demonstrated the power of his new theory with more elaborate and explicit exemplification than Kekule had done. He provided fully resolved formulas for ethane, for four different alcohols and four organic acids, and for more complex substances such as glycol, glycerin, tartaric acid, and glucose. In many of these formulas there appear, for the first time, dotted lines to symbolize connections between atoms. 

It was during this period from the second World War to around 1965 that the unique character of the phosphines and arsines as ligands was established. It was also during this period that the fundamentally important qualities of hydride and ligands attached through carbon to transition metals were discovered. Here it is not possible to do more than summarize these developments,t which are elaborated more fully where appropriate in other chapters. 

The synthesis of a fully functionalized cyclopentane core structure of pactamycin, a potent antitumor antibiotic, involves Overman rearrangement as a key reaction. Heating a mixture of potassium carbonate and the imidate derived from allylic alcohol 68 in p-xylene yields the desired trichloroacetamide 69 as a single isomer in 90% yield from 68. In this reaction, potassium carbonate is a crucial additive as no desired product is obtained when the same reaction is carried out without potassium carbonate. Trichloroacetimidate 69 has been elaborated into the tricyclic compound 70 which contains all the carbon atoms for the core cyclopentane of pactamycin,... 

A comparable range of heteronuclear shift correlation experiments is also available, with and without multiplet decoupling. Again, the spins are correlated by polarization transfer. A more elaborate homonuclear shift correlation experiment, INADEQUATE, may be performed to detect C- C connectivities and hence identify carbon frameworks. The elaborations involve double-quantum processes to eliminate the otherwise dominant signals from C bound to C. These and other methods are fully discussed by Sanders and by Ernst et a/. " ... 

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