engleski

Anion-induced aza-Michael addition of furfurylguanidines to dimethyl acetylenedicarboxylate

Cycloaddition of the furan derivatives to dimethyl acetylenedicarboxylate (DMAD) represents a highly atom-efficient approach to the oxanorbornadiene cage.1 DMAD is highly reactive as a dienophile but also sensitive to the attack of nucleophiles like amines, thiols, neutral guanidines, etc..2–4 Although guanidinium salts cannot be considered good nucleophiles, our preliminary investigations on the cycloaddition of guanidinium halides to DMAD indicated the formation of 2-aminoimidazolidin-4-one derivatives (aza-Michael reaction products) together with 2-halofumarate (Scheme). Herein, we present results of the aza-Michael addition of furfurylguanidines to DMAD triggered by the addition of the anion to DMAD and subsequent deprotonation of the guanidinium cation. The mechanism for the process is proposed and investigated by DFT calculations. The structural diversity of the products is interpreted in terms of the stability of guanidine tautomers and/or sterical hindrance of the alkyl groups.

aza-Michael addition ; DFT calculations ; furfurylguanidines ; imidazolidinone

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