Friedel-Crafts Reaction of Dimethyl 2-Oxopropylphosphonate and Diethyl 2,2-Diethoxyethylphosphonate With Electron-Rich Arenes

Dimethyl 2-oxopropylphosphonate and diethyl 2,2-diethoxyethylphosphonate react with electron-rich arenes such as phenol, anisole, 1,3-dimethoxybenzene, and 1-methylpyrrole in the presence of trifluoromethanesulfonic acid to afford β,β-diarylphosphonates in moderate to good yield. The minor products observed in some cases are β -aryl-α,β -unsaturated phosphonates.

Keywords:

• β-Ketophosphonate
• Friedel-Crafts reaction
• trifluoromethanesulfonic acid

Notes

^a Reactions carried out in dichloromethane (5 ml) and TfOH (4 mmole) at r.t. for 2 h.

^b Ratio of products was determined by ¹H and ³¹P-NMR analysis.

^c 1a was mainly (95%) 4,4′-isomer containing 5% of the 2.4′-isomer.

^d Reaction carried out in neat methanesulfonic acid (5 ml).

^e Pure (> 98%) 4,4′-isomer.

^f Mixture of 2,2′- and 2,3′-isomers (3:1).