Efficient formation of water- and air-stable aza-ylides has been achieved using the Staudinger reaction between electron-deficient aromatic azides such as 2,6-dichlorophenyl azide and triarylphosphines. The reaction proceeds rapidly and has been successfully applied to chemical modification of proteins in living cells.

A method for protecting organic azides from click reactions with alkynes is reported. Treatment of azides with Amphos affords phosphazides, which are stable under click reaction conditions and are easily converted back to azides by treatment with elemental sulfur. Thus, the method allows for facile modification of azide compounds via site-selective click reactions.

An efficient benzene ring construction method using oxadiazinones as a platform molecule has been developed. Sequential reactions of oxadiazinones with cycloalkynes and arynes afforded partially reduced polyaromatics. This method enables facile preparation of various unsymmetrical doublyring-fused benzene derivatives including multisubstituted tetrahydroanthracenes and anthracenes.

A facile method for preparing various functional cycloalkynes, including proteins incorporated with a cycloalkyne moiety, from the corresponding azides is developed. Treatment of diynes bearing strained and terminal alkyne moieties with a copper salt enabled terminal alkyne-selective click conjugation with azides, whereas a more azidophilic strained alkyne moiety was transiently protected from the click reaction via complexation with copper.

An efficient method for the reduction of aromatic azides to anilines via the Staudinger reaction using tri-n-butylphosphonium tetrafluoroborate with triethylamine in aqueous tetrahydrofuran solution is reported. The method enables the aromatic azido-selective reduction of 3-azido-5-(azidomethyl)benzene derivatives to efficiently afford anilines bearing an azidomethyl group.