Efficient Synthesis of Some New Spirochromens Containing Indoline Moiety

An Efficient and Concise Synthesis of N-3-Substituted 9-Methoxy-4H-[1]-benzopyrano[2,3-d]pyrimidine-4(5H)-imines and Form­amidine Derivatives from Methyl N-(3-Cyano-8-methoxy-4H-[1]-benzopyran-2-yl)methanimidate

“…Methanimidate and their formamide derivatives are well known as useful building blocks 8 in organic synthesis. 9 Methyl or ethyl methanimidates are usually synthesized from primary amines with trimethyl or triethyl orthoformate under reflux, but these usual methods suffer from some drawbacks including: the use of large excess of acid anhydride, 10 or acid, 11 long reaction time, and high reaction temperature 5 that result in decomposition of the starting reactants and the desired products. Selectivity appears to be a major problem according to this approach due to decomposition with the formation of symmetric N,N′-formamidines.…”