Carbofunctionalization of Terminal Alkynes via Rhodium Catalysis Enabling Formations of Four Different Bonds

Acid Promoted Tetrafunctionalization of Terminal Alkynes: Geminal Diazidation and Dibromination

The synthesis of complex alkanes by the tetrafunctionalization of alkynes is limited and challenging. Herein, an unprecedented efficient geminal diazidation and dibromination of terminal alkynes is developed, which provides novel access to structurally diverse organic azides. The approach has exclusive chemo- and regioselectivity and features mild reaction conditions, good tolerance of various functional groups, and more crucially, no metal involved in the reaction, thereby benefiting the late-stage decoration of medicinal molecules. A mechanistic study showed that the current geminal diazidation and dibromination proceeds via a radical pathway.

Rhodium and Isothiourea Dual Catalysis: Enantiodivergent Transformation of Terminal Alkynes

A dual rhodium/isothiourea catalytic system was developed for the enantiodivergent transformation of terminal alkynes. Under synergistic rhodium/isothiourea dual catalysis, terminal alkynes can be creatively utilized as precursors for C1-ammonium enolate species, which subsequently participate in [4 + 2] and [2 + 2] annulation reactions with α,β-unsaturated ketimines or ketones, respectively. A wide range of chiral lactams and lactones were obtained in excellent yields and stereoselectivities (up to >20:1 dr, 98% ee).

Thiocyanate promoted difunctionalization and cyclization of unsaturated C-C bonds to construct 1-sulfur-2-nitrogen-functionalized alkenes and 2-thiocyanate indolines

An unprecedented one-pot route to achieve highly regioselective 1-sulfur-functionalized 2-nitrogen-functionalized alkenes and 2-thiocyanate indolines from unsymmetrical ynamides (readily and generally available amides) using the commercially available inexpensive iodobenzene diacetate (PIDA) as the oxidant and potassium thiocyanate (KSCN) as the thiocyanate (SCN) source has been developed. The interconversion of thiocyanate (SCN) and isothiocyanate (NCS) groups simultaneously forms C-N and C-S bonds in this metal-free approach, while introducing important functional groups into homemade alkynes. A radical-chain mechanism, involving competing kinetically controlled chain transfer at the S atom and sterically-controlled chain transfer at the N atom of the thiocyanogen molecule in this mild approach, is proposed.