Design and synthesis of laser-activatable tetrazoles for a fast and fluorogenic red-emitting 1,3-dipolar cycloaddition reaction.

The design and synthesis of a new class of laser light activatable tetrazoles with extended π-systems is reported. Upon 405 nm laser light irradiation, these bithiophene-substituted tetrazoles underwent extremely fast 1,3-dipolar cycloaddition reactions with dimethyl fumarate with second-order rate constants approaching 4000 M(-1) s(-1). The resulting pyrazoline cycloadducts exhibited solvent-dependent red fluorescence, making these tetrazoles potentially useful as fluorogenic probes for detecting alkenes in vivo.