Styryl and functionalized aryl derivatives of lawsone through metal-free cross-coupling of its BF3-activated phenyliodonium ylide with cinnamaldehydes and arylaldehydes
Phenyliodonium ylide of lawsone activated with BF3 center dot Et2O reacts with cinnamaldehydes to afford 2-hydroxy-3-styryl-1,4-naphthoquinones in good to excellent yields and relatively high level of stereospecificity through deformylation of the aldehydes. The product yield is diminished with a methoxy substituted cinnamaldehyde and becomes zero with a dimethoxy substituted substrate giving rise to another product, 2-hydroxy-3-aryl-1,4-naphthoquinone. The reaction of the same ylide with salicylic aldehydes forms 2-hydroxy-3-(2-hydroxyary1)-1,4-naphthoquinones and/or benzo[d]naphtha[2,1-b]furano-5,6-diones, depending on the reaction conditions applied. Plausible reaction mechanisms explaining the formation of these products are proposed. The products showed potent antioxidant activity and inhibited lipoxygenase. (C) 2015 Elsevier Ltd. All rights reserved.
Fieser et al., Journal of the American Chemical Society, 1948, vol. 70, p. 3177
作者:Fieser et al.
DOI:——
日期:——
Pd(II)-Catalyzed Synthesis of Alkylidene Phthalides via a Decarbonylative Annulation Reaction
An unprecedented Pd(II)-catalyzed decarbonylative C–H/C–C activation and annulationreaction, which proceeds via intramolecular cyclization, is reported. This reaction of hydroxynaphthoquinones with disubstituted alkynes provides good yields of substituted alkylidene phthalides, which are the key intermediates for the synthesis of bioactive natural products.