Assembly of (2×C₂+C’₂)×n Molecular Complexity Using a Sequence of Pt- and Pd-Catalyzed Transformations with Calcium Carbide

Graphical Abstract

This study presents synthetic approaches within CaC₂ chemistry, introducing the 2×C₂-to-C₄ and (2×C₂+C’₂)×n assembly concepts. Using Pt catalysis, carbon from two calcium carbide molecules was transferred to an organic C₄ fragment. Supplemented with Pd catalysis, the described methodology offers a novel pathway for controlled molecular assembly and polymer synthesis.

Abstract

Constructing molecular complexity from simple precursors stands as a cornerstone in contemporary organic synthesis. Systems harnessing easily accessible starting materials, which offer control over stereochemistry and support a modular assembly approach, are particularly in demand. In this research, we utilized calcium carbide, presenting a sustainable pathway to generate acetylene gas – a fundamental C₂ building block. We performed a Pt-facilitated linkage of two C₂-units sourced from two calcium carbide molecules to craft a conjugated C₄ core with exceptional stereoselectivity. As a benchmark, we selected the synthesis of (E,E)-1,4-diiodobuta-1,3-diene, executing it in a two-chamber reactor. Compartmentalization of the reactions across these chambers resulted in the desired product in 85% yield. Furthermore, high-energy polymeric substances were derived by marrying the molecular intricacy between (E,E)-1,4-diiodobuta-1,3-diene and calcium carbide, underpinning a unique C₄+C₂ assembly blueprint. The structure and morphology of the polymeric material were characterized by IR and NMR spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Overall, two complementary 2×C₂-to-C₄ and (2×C₂+C’₂)×n assembly schemes were developed using Pt and Pd catalysis.