La-based perovskite structures as efficient heterogeneous catalysts for acceptorless dehydrogenative coupling of alcohols and amidines toward pyrimidines

Abstract

The synthesis of fine chemicals using biomass-derived reagents has already emerged as one of the most urgent challenges, for which, many alternative green approaches to the well-known organic transformations need to be developed. In line with this concept, a novel green process for the heterogeneous catalytic acceptorless dehydrogenative coupling (ADC) of benzamidine and biomass-derived alcohols to pyrimidines is presented in this work. In contrast to the well-established heterogeneous Pt/C catalysis (EcoScale of 64) operating under harsh reaction conditions, we are able to build a green process (EcoScale of 81) based on the use of LaCoO₃ perovskite catalyst allowing an exclusively selective (84% isolated yield of pyrimidine) cyclization at ∼80 °C within only 8 hours even in a green solvent (2-Me-THF). In addition, the structure–activity relationship of this catalyst was also successfully uncovered, showing a cooperatively acting catalyst. In particular, the La(III)–O²⁻ sites can govern the activity of the catalyst, while the Co(III)–O²⁻ centers dictate the selectivity of the perovskite. Furthermore, the LaCoO₃ structure proved to be a recyclable and highly substrate-tolerant promoter, which is essential for producing substituted pyrimidines.