A divergent McMurry coupling of the bis-salisaldehyde with methylene linker: The characterization of a key by-product with the possible pathway formation

The McMurry coupling of a bis-salisaldehyde 3a with methyl linker as the smallest member of its alkyl series is known to give the remarkably lower yield of the corresponding stilbenophanes. The half part of this molecule, unlike bigger analogues, is a good leaving group which affordsthreo isomer of 4H, 4′H–4,4′-bibenzo[d][1,3]dioxine 4 in high diastereoisomeric ratio (99>). A further study showed that the formation of this key by-product is the reason for formation of other by-products, namely, 5a,10b-dihydrobenzofuro[2,3-b]benzofuran 9 and 2-(2,3-dihydrobenzofuran-2-yl)phenol 10. Two reaction pathways for the formation of by-products have been proposed which are responsible for the unusual activity of dialdehyde 3a.