Facile synthesis of 4H-chromene derivatives via base-mediated annulation of ortho-hydroxychalcones and 2-bromoallyl sulfones

• Srinivas Thadkapally,
• Athira C. Kunjachan and
• Rajeev S. Menon

Beilstein J. Org. Chem. 2016, 12, 16–21, doi:10.3762/bjoc.12.3

• furnished 3-arylsulfonyl-4H-chromene derivatives in 58–67% yield (18 examples). 2-Bromoallyl sulfones functioned as synthetic surrogates for allenyl sulfones in the reaction. Keywords: allenes; chromenes; cyclocondenzation; sulfones; vinylic substitution; Findings Benzo[b]dihydropyran, commonly known as

• ], multicomponent reactions [8], ring-closing metathesis approaches [9][10], tandem reactions of 1,3-dicarbonyl compounds [11][12] and cyclocondenzation reactions of salicylic aldehydes with α,β-unsaturated carbonyl compounds [13][14][15]. The utility of some of these methods are limited by drawbacks such as

• -mentioned reactions (Scheme 1, path d) [24]. The facile cyclocondenzation of salicylaldehyde with 2a (Scheme 1, path c) prompted us to explore analogous annulation reactions for the synthesis of functionalized chromene derivatives. The biological activities exhibited by many 4H-chromene derivatives provided