Direct access to 2-(N-alkylamino)pyrimidines via ruthenium catalyzed tandem multicomponent annulation/N-alkylation

Abstract

2-(N-alkylamino)pyrimidines are important heterocycles widely found in various pharmaceutically important drugs. Here, we have disclosed a new cooperative ruthenium complex catalyzed tandem multicomponent synthesis of 2-(N-alkylamino)pyrimidines directly from guanidine salt and alcohols. The reactions proceeded through the dehydrogenation of alcohols, followed by CC coupling and sequential CN coupling with guanidine and primary alcohol, with the elimination of three equivalents of hydrogen gas. In this work, application of both the acceptorless dehydrogenative coupling (ADC) and borrowing hydrogen (BH) strategies were accomplished in a single reaction. This catalytic method tolerated a wide range of substrates. The viability of the current method was demonstrated by preparative scale synthesis of a few products. A plausible catalytic cycle was proposed based on various control experiments, mechanistic studies and DFT calculations. Remarkably, 42 new 2-(N-alkylamino)pyrimidines were synthesized following this catalytic protocol.