Simultaneous construction of the polymer backbone and side chains by three‐component polycondensation: The synthesis of polyurethanes with allyl side chains from dialdehydes, alkylene N,N′‐bis(trimethylsilyl) carbamates, and allyltrimethylsilane

Polyurethanes with allyl side chains were synthesized by the simultaneous acid‐catalyzed reaction of dialdehydes (1), alkylene N,N′‐bis(trimethylsilyl) carbamates (4), and allyltrimethylsilane (5). When 5 was added to a mixture of 1, 4, and the catalyst, a low molecular weight polymer was formed, as well as a large amount of an insoluble gel. However, when a mixture of 1, 4, and 5 was added to the catalyst, the formation of gel was depressed, and the desired polyurethanes, consisting of 1, 4, and 5 in a molar ratio of 1/1/2, were obtained in good yields. This polyurethane synthesis is unusual in that it concurrently constructs both the polymer backbone and the functional side chains from three starting compounds.