Recent Progress in the Synthesis of Heterocycles through Base Metal‐Catalyzed Acceptorless Dehydrogenative and Borrowing Hydrogen Approach

Abstract

Development in the area of acceptorless dehydrogenation (AD) and borrowing hydrogen (BH) catalysis emerge as one of the potential tools for various CÀ C and C-heteroatom bond forming reactions. Alcohols, which are important lignocellulosic biomass products, act as pivotal electrophilic coupling partners in such processes and interestingly only H 2 or H 2 O is eliminated as a byproduct. Initially, the area was developed by the use of noble metal catalysts. Recently, base metals such as Mn, Fe, Co, and Ni proved to be environmentally benign and inexpensive alter-natives for the noble metals in the application of AD and BH methods. This transition metal catalyzed AD and BH approaches also allow access toward a plethora of structurally important heterocyclic molecules via environmentally benign and atom economical strategy. Herein, we summarize the current and rising expansion of base metal catalyzed heterocycles synthesis through acceptorless dehydrogenation and borrowing hydrogenation strategy.

Well-Defined Phosphine-Free Manganese(II)-Complex-Catalyzed Synthesis of Quinolines, Pyrroles, and Pyridines

“…The development of sustainable catalytic systems for alcohol dehydrogenation and related coupling reactions using earth-abundant transition metals is exciting and highly desirable. − In the past decade, significant progress has been made on 3d transition-metal (Fe, Co, Mn, Ni, etc. )-catalyzed alcohol dehydrogenation and associated reactions because of its higher abundance, lower toxicity, and lesser cost of these metals.…”

Well‐Defined Ni−SNS Complex Catalysed Borrowing Hydrogenative α‐Alkylation of Ketones and Dehydrogenative Synthesis of Quinolines

“…The applicability of Mn and Co complexes towards this transformation was also demonstrated by the group of Beller, Zheng and others [13] . The complexes reported mostly possess either air sensitive phosphine‐based ligand or sophisticated ligand framework which needs tedious synthetic procedures/sophisticated storage and handling procedures [14] . Recently, the applicability of nickel for AD and BH transformations has been perceived because of its low cost and high natural abundance [15] .…”

Lemon Juice: A Versatile Biocatalyst and Green Solvent in Organic Transformations

“…For example, the use of metals or metal complexes as catalysts has contaminated water bodies, causing toxic effects to aquatic life and plants, further disrupting the food chain. In addition, most of these metals or metal complexes are expensive and commercially non‐viable [2a–d] . Therefore, the development of alternative, greener/eco‐friendly methods with less hazardous reaction conditions, has received significant research attention in organic synthesis and industrial manufacturing [3] .…”