4-Diazomethyl-7-methoxycoumarin

Reaction of 3-acetylcoumarins with Vilsmeier reagents has given propeniminium salts (154) which are useful intermediates.165 4-Diazomethyl-7-methoxycoumarin is unexpectedly stable and does not react with alcohols or phenols but with carboxylic acids, it yields... 

Diazomethyl-7-methoxycoumarin is a rather stable reagent which allows convenient derivative formation carboxylic acids form esters by heating in acetonitrile. With alcohols, fluorescent ethers are obtained in dichlo-romethane in the presence of HBF4 as catalyst [477]. 

Other reagents used are 4-bromomethyl-7-ace-toxycoumarin (BrMAC), 3-Bromoacetyl-7-methoxy-coumarin (BrAMC). The use of BrAMC allows the derivatization of fatty acids at room temperature. BrAMC has a higher reactivity than other bromomethylcoumarins 4-bromomethyl-6,7-dimethoxycoumarin, 4-bromomethyl-6,7-methylene-dioxycoumarin, 4-bromomethyl-7,8-benzocoumarin, 4-diazomethyl-7-methoxycoumarin, and 7-(diethyl-amino)-coumarin-3-carbohydrazide. 

Sulfonic adds have largely remained unexplored in terms of a functional group that is released from a photoremovable protecting group. One recent example has been reported by Bendig et in which methanesulfonic acid was protected as the corresponding methoxycoumarin derivative. (7-Methoxycou-marin-4-yl)methylmethanesulfonate 59 was synthesized from reaction of methanesulfonic add with 4-(diazomethyl)-7-methoxycoumarin in refluxing chloroform. Photolysis at 333 nm resulted in the release of methanesulfonic acid, as shown in Eq. (69.30). 

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