Patent ID: 8273885

Claim:
A fluoroboron compound or a salt thereof, wherein said fluoroboron compound or the salt thereof is capable of forming a cyclic ether fused with an aromatic ring by an intramolecular alkoxymethylation reaction, wherein said fluoroboron compound is represented by the following formula (I): (wherein the moiety represented by the formula represents an aromatic ring which may or may not have substituents other than L and —R—O—CH 2 BF 3 M groups, wherein said aromatic ring is selected from the group consisting of benzene, naphthalene, pyridine and quinoline; L represents a leaving group selected from the group consisting of a halogen atom, a substituted alkylsulfonyloxy group, an unsubstituted alkylsulfonyloxy group, a substituted arylsulfonyloxy group and an unsubstituted arylsulfonyloxy group; R represents a substituted or unsubstituted alkylene group of 1 or 2 carbon atoms; M represents an alkali metal cation, [N(R 1 )(R 2 )(R 3 )(R 4 )] + , or [P(R 1 )(R 2 )(R 3 )(R 4 )] + , (in which R 1 , R 2 , R 3 , and R 4 each independently represents a C 1-6 alkyl group or a C 7-16 aralkyl group); with the proviso that L and —R—OCH 2 BF 3 M are respectively located on contiguous carbon atoms on the aromatic ring or, in the case where the aromatic ring is a fused aromatic ring formed of 2 rings, on two carbon atoms adjacent to one carbon at the fused position.