General and Chemoselective Bisphosphonylation of Secondary and Tertiary Amides

With Tf₂O as the activation reagent, a mild and general method has been developed for the bisphosphonylation of both secondary and tertiary amides. The protocol is highly efficient and chemoselective, and it tolerates a number of sensitive functional groups such as cyano, ester, and aldehyde groups

A Light-Gated Molecular Brake with Antilock and Fluorescence Turn-On Alarm Functions: Application of Singlet-State Adiabatic Cis → Trans Photoisomerization

A light-gated molecular brake that displays both high braking power (∼10⁷) and high switching power (∼74%) is reported. The lower rate for brake-on than for brake-off switching of the pentiptycene rotor mimics the function of an antilock braking system (ABS) for vehicles on a loose surface. The brake is also armed with a fluorescence turn-on alarm for accidental deactivation of the ABS function by acids. All of these features are associated with the highly efficient singlet-state adiabatic cis → trans photoisomerization of the phenylstilbene chromophore

An Antilock Molecular Braking System

A light-driven molecular brake displaying an antilock function is constructed by introducing a nonradiative photoinduced electron transfer (PET) decay channel to compete with the trans (brake-off) → cis (brake-on) photoisomerization. A fast release of the brake can be achieved by deactivating the PET process through addition of protons. The cycle of irradiation–protonation–irradiation–deprotonation conducts the brake function and mimics the antilock braking system (ABS) of vehicles