abstract
The synthesis, characterization, and catalytic application of a new phosphine-free, well-defined, water-soluble, and air-stable Mn(II)-catalyst [Mn(L)(H2O)(2)Cl](Cl) ([1]Cl) featuring a 1,10-phenanthroline based tridentate pincer ligand, 2-(1H-pyrazol-1-yl)-1,10-phenanthroline (L), in dehydrogenative functionalization of alcohols to various N-heterocycles such as quinazolin-4(3H)-ones, quinolines, and quinoxalines are reported here. A wide array of multisubstituted quinazolin-4(3H)-ones were prepared in water under air following two pathways via the dehydrogenative coupling of alcohols with 2-aminobenzamides and 2-aminobenzonitriles, respectively. 2-Aminobenzyl alcohol and ketones bearing active methylene group were used as coupling partners for synthesizing quinoline derivatives, and various quinoxaline derivatives were prepared by coupling vicinal diols and 1,2-diamines. In all cases, the reaction proceeded smoothly using our Mn(II)-catalyst [1]Cl in water under air, affording the desired N-heterocycles in satisfactory yields starting from cheap and readily accessible precursors. Gram-scale synthesis of the compounds indicates the industrial relevance of our synthetic strategy. Control experiments were performed to understand and unveil the plausible reaction mechanism.
keywords
CATALYZED ALPHA-ALKYLATION; ACCEPTORLESS DEHYDROGENATION; ENVIRONMENTALLY BENIGN; BORROWING HYDROGEN; MANGANESE COMPLEX; PRIMARY ALCOHOLS; PINCER COMPLEX; AMINES; KETONES; QUINAZOLINONES
subject category
Chemistry
authors
Mondal, S; Chakraborty, S; Khanra, S; Chakraborty, S; Pal, S; Brandao, P; Paul, ND
our authors
Paula Cristina Ferreira da Silva Brandão
Assistant ResearcherProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
acknowledgements
The research was supported by MoE, Govt. of India (Project MoE/STARS/2023-0450) and CSIR (Project: 01(3023)/21/EMR-II). S.M., S.C., S.C., and S.P. thank IIESTS and S.K. thanks CSIR for fellowship support. Financial assistance from IIESTS is acknowledged. DST sponsored SAIF, IIESTS is acknowledged for providing HRMS, GC, and NMR facilities. Paula Brandao gratefully acknowledges the financial support of this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC).