A Chan–Evans–Lam approach to trisubstituted vinyl ethers

Abstract

Trisubstituted vinyl ethers were accessed via Chan–Evans–Lam coupling of vinyl trifluoroborates and primary aliphatic alcohols. This approach complements prior methods that required the use of neat liquid alcohol coupling partners....

Recent advances in Chan–Lam coupling reaction

“…Wulff and colleagues opened up an avenue for the construction of vinyl ethers possessing three substituents. 64 This mild Chan–Lam coupling between primary aliphatic alcohols and vinyl trifluoroborates in the presence of 20 mol% Cu(OAc) 2 and 40 mol% DMAP using 4 Å MS in an O 2 atmosphere at room temperature for 48 h in DCM furnished the products in reasonable to good yields (Scheme 61). Besides this, in the case of benzyl vinyl ethers, treatment with 50–80% NaBH 4 was necessary to remove the background oxidation product.…”

Synthesis of 1-Methylcyclopropyl Aryl Ethers from Phenols Using an Alkenylation-Cyclopropanation Sequence

“…To our surprise, the preparation of these substrates using Chan-Evans-Lam conditions was unknown. The closest example we could find was one reported by Wulff who transferred a dihydropyran moiety to a phenol using a cyclic potassium trifluoroborate reagent . When applied to phenol 3a , Wulff’s conditions gave the desired product 9a in only 20% yield (Scheme ).…”

“…Interestingly, the vinylation is selective for phenols over alcohols ( 9u ). This was unexpected since Wulff reported the O-alkenylation of alcohols using very similar conditions . In the case of 3-hydroxypyridine, the amount of 4-(dimethylamino)­pyridine (DMAP) had to be lowered to obtain a decent yield of 9w , possibly due to the pyridine acting as a ligand for the copper.…”

“…The closest example we could find was one reported by Wulff who transferred a dihydropyran moiety to a phenol using a cyclic potassium trifluoroborate reagent. 21 When applied to phenol 3a, Wulff's conditions gave the desired product 9a in only 20% yield (Scheme 4). Mobashery used very similar conditions for the O-styrylation of phenols.…”