Poly(vinyl amine) (PVAm) reacts with acetone in aqueous solution. It generates imine and aminal moieties along the PVAm backbone. The molecular structure of acetone‐modified PVAm is confirmed by liquid 1H and 13C as well as solid state 13C NMR and ATR‐FTIR spectroscopies. Model compounds produced from 1,3‐diaminopropane with acetone in chloroform are used to assign the solid state 13C NMR signals of the modified polymer. Quantitative elemental analysis of acetone‐modified PVAm samples supports the analytical results. The mechanism of the imine and aminal formation is discussed with regard to the anomeric stabilization of the incipient hemiaminal intermediate. The rapid and unexpectedly favorable formation of PVAm acetone hemiaminal, acetone imine, and aminal formation has implications for the conduct of PVAm research and even the interpretation of prior published results. As acetone was often used in the past to precipitate waterborne PVAm derivatives, this finding has a severe impact on the interpretation of research results. The consequences and the revised interpretation of selected publications are discussed.

Cyclooctyne and cycloocten-5-yne undergo, at room temperature, a 1,3-dipolar cycloaddition with dialkyl acetylenedicarboxylates 1a,b to generate furan-derived short-lived intermediates 2, which can be trapped by two additional equivalents of 1a,b or alternatively by methanol, phenol, water or aldehydes to yield polycyclic products 3b-d, orthoesters 4a-c, ketones 5 or epoxides 6a,b, respectively. Treatment of bis(trimethylsilyl) acetylenedicarboxylate (1c) with cyclooctyne leads to the ketone 7 via retro-Brook rearrangement of the dipolar intermediate 2c. In all cases, the products are formed with perfect atom economy.

The free radical copolymerization of N‐vinylformamide (NVF) with methylvinylketone in water and the subsequent alkaline or acidic hydrolysis produce iminium structures containing polymers. It can be concluded from the copolymerization parameters (rN ‐vinylformamide = 0.02, r methylvinylketone = 0.50) that alternating copolymers are formed which contain few amounts with statistically arranged monomer sequences. The acidic hydrolysis of the copolymer results in a water‐soluble polymer bearing five‐membered iminium rings along the polymer chain. A water‐insoluble polymer is generated under alkaline conditions also containing five‐membered imine rings. The formation of the iminium ring polymer is attributed to the fact that generated free amino groups derived from NVF immediately react with the keto groups in the vicinity. The molecular structures of the obtained polymers are characterized by 1H‐NMR, 13C‐NMR, and IR spectroscopy. The assignment of the signals in the novel polymers are confirmed by model compounds.