1-acylsemicarbazides by ring opening of iminodiaziridines with carboxylic acids: Novel, expeditious access to the azapeptide motif
Carboxylic acids react rapidly and quantitatively with iminodiaziridines to afford 1,2,4-trisubstituted 1-acylsemicarbazides in a multistep sequence. In this way, a carboxy group is readily converted into an azapeptide motif. Broad signals in high-field H and C NMR spectra recorded for the products are indicative of dynamic processes. Georg Thieme Verlag Stuttgart New York.
Quast, Helmut,Schmitt, Edeltraud,Ross, Karl-Heinz
experimental part
p. 3358 - 3362
(2010/11/16)
Thermolysis, Photolysis, and Acid Catalysis of an α-(Dimethylamino)azoalkane. Amino Stabilization of a Carbon Radical Center
The unsymmetrical azoalkane 2-(tert-butylazo)-2-(dimethylamino)propane (7) has been synthesized cleanly by nucleophilic displacement of chloride from the corresponding α-chloroazoalkane 5 with dimethylamine.Thermolysis of 7 in hydrocarbon solvents affords typical radical-derived products and exhibits activation parameters ΔH(excit.) = 26.6 +/- 0.4 kcal/mol and ΔS(excit.) = -6.6 +/- 1.1 eu.Since the thermolysis rate of 7 is 104 faster than that of 1,2-di-tert-butyldiazene, the large stabilization of α-amino radicals is supported.Unusual products were obtained in acetonitrile, suggesting reduction of the azo linkage by 2-(dimethylamino)-2-propyl radicals and cleavage of the resulting hydrazyl radicals.In protic solvents, 7 undergoes acid catalyzed decomposition via tert-butyldiazene as a postulated intermediate.
Engel, Paul S.,Wu, Wen-Xue
p. 2720 - 2725
(2007/10/02)
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