2-Amino-4,5-dihydro-3-furancarboxylates

The reaction of 2-amino-4,5-dihydro-3-furancarboxylic esters (51) with amines appears interesting85. In contrast to the structure assigned earlier86-88, the reaction products have been later identified as 1,1-enediamines attached to a lactone moiety85. Thus, substrate 51 reacts with methylamine to give acyclic 1,1-enediamines 52 with an approximate E/Z ratio of 40 60. The reaction involves 4,5-dihydrofuran ring-opening and lactone-formation steps (Scheme 3). In the case of ethylenediamine and 1,3-diaminopropane, the reaction of 51 leads to the formation of cyclic 1,1-enediamine... 

Reaction of alkanediamines 230 with ethyl 2-amino-4,5-dihydro-3-furancarboxylates (8 X = O, n = 1) does not give furo [2,3-e]-1,4-diazepine-5-ones 231.133,134 Instead, as high-resolution 13C-NMR spectra show, in a sequence of addition and elimination steps (232-233), 3-(2-imidazolidinylidene)- and 3-(hexahydro-2-pyrimidinylidene)dihydro-2-(3//)-furanones 234 are formed135 (Scheme 60). The constitutions of 234 were confirmed by 13C-NMR gated decoupling.135... 

A freshly prepared acetonic solution of 1,4-phthalazinequinone (171) with ethyl 2-amino-5-methyl-4,5-dihydro-3-furancarboxylate (172) gave 2-(3-ethoxy-carbonyl-2-imino-5-methyltetrahydrofuran-3-yl)-1,4(2//,370-phthalazined-ione (173) (AcOMe, -30°C 20°C, 30 min 76%). ... 

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