Journal Article

Gaseous sulfurdioxide reacts with 1,1-dimethylhydrazine, N-aminopiperidine, N-aminohomopiperidine, and N-aminomorpholine to form 1:1 adducts. The adducts are formed between the nitrogen atom of the R2N group in the hydrazine and the sulfur atom in sulfurdioxide. Analytical, proton NMR and i.r. spectral data are given.

Some new cyanoacetates were synthesized and characterized. They are precursors for α-cyanoacrylates used as rapidly polymerized, cold-hardening adhesives.

Alicyclic mono and diacrylates from alpha-pinene and beta-pinene derivatives were synthesised and characterized spectroscopically. They were then compounded in alkyl 2-cyanoacrylate adhesives as crosslinkers. Their effect on the adhesive bond strengths after exposing the adhesive bonds to various temperatures, was studied.

Polyalkyl 2-cyanoacrylates begin to retropolymerize and deteriorate dramatically at temperatures above 80°C. They bond rapidly to the metal surfaces and readily lose strength even at ambient temperatures. These two drawbacks of the cyanoacrylates have made this class of adhesives unpopular as structural adhesives. Several attempts have been made to increase the thermal stability and the stability of the bond between the metal surfaces by adding chemicals like cyclopentadienoates and anhydrides to the cyanoacrylates.

Some alkenyl- and alkinyl-2-cyanoacrylate monomers, possessing adhesive properties were synthesized. The ease of esterification of cyanoacetic acid, the first step of the synthesis, with some alcohols was in the following order:

The tacticity assignments from the literature for the 13C-NMR signals of the side-chain methylene group of poly(ethyl cyanoacrylate) are reversed, and new assignments of the main-chain methylene group are proposed. The assignments were made possible by a combination of DEPT and HETCOR NMR experiments on samples of varying microstructure distributions. The polymer tends toward syndiotacticity, not isotacticity as previously reported. The distribution of stereoisomers fits well to a Bernoulian statistical model.

Polycyanoacrylates were found to be inherently unstable. Even in the absence of a deliberately added strong base, their molecular weights decreased drastically on standing in solution in accord with observations by Ryan and McCann (Makromol Chem Rapid Commun 1996, 17, 217). The initial high molecular weight polymer disappeared over the course of a few hours in solution and was replaced by a much lower molecular weight material.

Die Synthese von purin-ähnlichen biheterocyclischen Ringsystemen wird beschrieben und insbesondere der Aufbau von verschieden substituierten Pyrazolo[3.4-d] pyrimidinen ausgehend von Pyrazolen oder Pyrimidinen besprochen. Synthesewege für Pyrazolo[3.4-c] pyridazine und Pyrazolo[3.4-b] pyridine ausgehend von Pyridazinen und Pyridinen und von Pyrazolo[3.4-b] pyrazinen und Pyrazolo[3.4-d] triazinen ausgehend von Pyrazolen werden angegeben. Als biheterocyclisches Ringsystem mit zwei kondensierten 6-Ringen werden die Pyrimido[4.5-d] pyrimidine erwähnt.