A. Bagno, W. Kantlehner, G. Saielli
Jul 1, 2008
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Journal
Journal of Physical Organic Chemistry
Abstract
We present an NMR and DFT investigation of the reaction of phenyl formate with 3-methoxyphenol and 3,5-dimethoxyphenol with excess BCl3. The products obtained (3-methoxy- and 3,5-dimethoxy-salicylaldehyde, respectively) are the same as those resulting from the Fries rearrangement of 3-methoxy- and 3,5-dimethoxy-phenyl formate. These results represent a novel regioselective synthetic route to aromatic aldehydes, using phenyl formate as a source of formylating agent. They also unambiguously prove that the Fries rearrangement of aryl formates (that we recently investigated in J. Org. Chem. 71, 9331–9340, 2006) is intermolecular: the intermediate formyl chloride is released in situ and, in turn, it formylates the intermediate dichloroborate ester of 3-methoxy- and 3,5-dimethoxy-phenol in a second independent step. The BCl2 moiety bound to the aryl oxygen of the substituted phenol interacts with the formyl chloride strongly favouring the ortho substitution. Copyright © 2008 John Wiley & Sons, Ltd.