Pd(0)/iodide salt-mediated Heck reaction of aryl nonaflates: Application to the synthesis of 2-(1-alkenyl)phenylphosphonates

Iodide salt, such as NaI, KI or n-Bu4NI (TBAI), rather than bromide or chloride salt, was found to play a key role in the Pd(0)-catalyzed Heck reaction of aryl nonaflates and terminal alkenes. In the presence of PdCl2(PPh3)2, NaI or TBAI in DMF, a class of 2-(1-alkenyl)phenylphosphonates was first synthesized via the reaction of o-phosphonylphenyl nonaflates with alkenes, the yields, regioselectivities and stereoselectivities were much dependent on the nature of the substituents. In case of the aryl nonaflates without bearing the sterically hindered phosphonyl group with the alkenes, the reactions proceeded more smoothly under the same conditions, leading to the linear products regioselectively in good to excellent yields. A rationale for this reaction is discussed.

In the presence of PdCl2(PPh3)2 and iodide salt, the aryl nonaflates with or without an ortho-phosphonyl group could proceed the Heck reaction to produce the desired alkenes.Figure optionsDownload as PowerPoint slideHighlights
• The existence of a bulky phosphonyl group at the ortho position of aryl nonaflates makes the nonaflates difficult to proceed the Heck reaction under classical conditions. Iodide salt rather than bromide or chloride salt was found to make the above Pd(0)-catalyzed Heck reaction take place.
• Using PdCl2(PPh3)2/iodide salt catalytic system, a series of 2-(1-alkenyl)phenylphosphonates were synthesized for the first time.
• 2-(1-Alkenyl)phenylphosphonates have considerable potential as useful intermediates for the following cyclization reactions.