増田 涼介

The synthesis, structural characterization in the solid state, and reactivity of a selenazolidine and a six-membered-ring derivative, i.e., a 1,3-tetrahydroselenazine, that contain a C6F5 substituent are reported. The first crystallographic characterization of a 1,3-tetrahydroselenazine was accomplished by means of single-crystal X-ray diffraction analysis. Despite the structural analogy to C6F5-substituted imidazolidines, these selenium-containing heterocycles exhibit pronounced thermal stability and high resistance toward the formation of the corresponding (amino)(seleno)carbenes, highlighting fundamentally different reactivity patterns between imidazolidines and selenazolidines.

Although various types of selenoamides have already been developed, examples of derivatives bearing a third heteroatom that acts as a second reactive center have remained limited so far. Recently, we reported the synthesis, structure, and fundamental reactivity of (selenocarbamoyl)phosphines, which exhibit ambident reactivity at two principal sites, i.e., the phosphorus and selenium atoms, in reactions with electrophiles. Herein, we report the synthesis of the first crystalline (phosphino)(seleno)iminium salt from a (selenocarbamoyl)phosphine, as well as the double-functionalization of (selenocarbamoyl)phosphines. Notably, the critical importance of the selenium atom for chalcogen-selective methylation was corroborated by a combined experimental and theoretical comparison with its sulfur analogue. Furthermore, the transition-metal complex of a (selenocarbamoyl)phosphine, whose phosphorus and selenium atoms were modified to give the phosphine selenide and the palladium complex, was obtained as a double-functionalized product.

A palladium-catalyzed and photoinduced coupling reaction between acylsilanes and allylic alcohol derivatives based on the reactions of nucleophilic siloxycarbenes, generated via the light-induced isomerization of the corresponding aroyl-, heteroaroyl-, alkenoyl-, or alkanolysilanes, with electrophilic π-allylpalladium complexes was developed. The dual activation by light and Pd(0) enables the coupling to proceed at temperatures below ambient temperature with a broad substrate scope and high functional-group tolerance.