. . . "The leaving group to be converted from Y1 in formula (VI) includes, for example, a halogen atom such as a chlorine atom, a bromine atom or an iodine atom; an organic sulfonyloxy group such as a methanesulfonyloxy group, an ethanesulfonyloxy group, a trifluoromethanesulfonyloxy group, a p-toluenesulfonyloxy group et al." . . .