Organic Synthesis of Ancient Windmill-Like Window Nanogrid at Molecular Scale

A series of the windmill-like fluorenoid nanogrid were synthesized by BF₃·Et₂O-mediated Friedel–Crafts reaction. Two typical routes to synthesize square windmill-like nanogrid (WG4) were developed. A one step synthesis using an I-shaped building block with a yield of 18 % and by-products of triangular nanogrid (WG3) and pentagon nanogrid (WG5) as well as multi-step synthesis using an l-shaped building block with a higher total yield of 53 %. Meanwhile, two isomers were separated for the triangle nanogrids (WG3), one of which has been confirmed by single-crystal X-ray diffraction.