Abstract
We have found amides of which C (O) -N bonds are extremely twisted. The structures were elucidated by 13C NMR, IR and UV spectroscopies, and X-ray analysis. Since the twisted amides are highly reactive compared to the planar ones, these were used for the acylation of hydroxy groups under neutral conditions. In the reaction of diols containing primary and secondary hydroxy groups with the amides, the primary one was selectively acylated. For diols containing alcoholic and phenolic hydroxy groups, the acylation selectively gave the corresponding alkyl esters. Furthermore, axially chiral twisted amides served as asymmetric acylating agents for sec-alcohols. We also investigated the effects of the C (O) -N bond rotation of the amides on the 13C, 15N, and 17O NMR chemical shifts, and IR carbonyl absorption. As the twist angle increased, the δ13C, δ17O and vC=o values increased, whereas, the δ15N value decreased. It was also found that the 13C (O) -15N coupling constants depend on the twist angles.The 1JC (O) , N value decreased with increasing twist angles.
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