The alcoholysis of diazasilacyclopentenes 2, easily obtained from glyoxaldiimines 1 with alkali metal and dichlorosilanes, gives either 3-amino-substituted pyrroles 4 or, with only small amounts of alcohol, N-substituted dihydropyrrolo[3,2-b]pyrroles 5. Reduction of 1 with hydrogen in ethanol in the presence of small amounts of a Pd/C catalyst also gives 4 and 5, together with smaller quantities of a 3,4diaminopyrrole 7. With more of the catalyst the formation of the 1,2-diaminoethanes 6 predominates. A single-crystal X-ray diffraction study was performed for the N,N'-di-tert-butyl derivative 5a, which confirms the expected centrosymmetric structure.
This paper reports the way different combinations of organic acids and tertiary amines work as catalysts in various polyurethane systems. The term "delayed action" is defined with examples of model reactions and commercially available polyurethane formulations. The effects on the reaction parameters in several foam systems and one elastomeric formulation will be presented. From amongst the broad range of amine catalysts we chose the following for our study: * 33.3% solution of triethylene diamine in dipropylene glycol THANCAT TD 33 A ## * methylazanorbornane as pure substance THANCAT AN 10 or a 33.3% solution in dipropylene glycol ##
Starting from glyoxaldiimines (I) and (VIII), the title compounds (II), (III), (VII) and (IX) can be obtained either directly by hydrogenolysis and/or via the silaheterocycle (VI) (already described).
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