The Substitution of Aryl Iodides with Cuprous Acetylides. A Synthesis of Tolanes and Heterocyclics¹

Total synthesis of natural products containing benzofuran rings

“…A key feature of this synthetic program was the conventional coupling reaction 112 between the copper acetylide 32 (ref. 113) and the aryl bromide 33, 114 generating as anticipated the benzofuran 34 with the desired skeleton. Finally, aer several steps, hydrolysis of 35 provided the target molecule 6, which was identical in all aspects to the natural XH-14 6 (Scheme 7).…”

Non‐carrier‐added 186, 188Re labeled 17α‐ethynylestradiol: A potential breast cancer imaging and therapy agent

“…In order to obtain the polymer-bound estradiol conjugate,ethynylestradiol 1 is coupled to 4-iodophenyl hydrazine2 according to Sonogashira (6) in the presence of a palladium-catalyst (7,8). The free hydrazine 3 is then attached to Tentage1 carboxy resin using ( 1 -benzotriazolyl)oxy tris(pyrro1idino) phosphonium hexafluorophosphate (PyBOP) and diisopropylethylamine in dichloromethane to give the corresponding solid-supported acetyl hydrazine derivative 4, which is separated from the reaction mixture.…”

Bioconjugation of Peptides by Palladium-Catalyzed C−C Cross-Coupling in Water

“…Moreover, a high reactivity (rate constant) is mandatory in order to allow the bimolecular coupling to take place at the very small molar concentrations of the biopolymers within reasonable periods of time. Here we report that the palladium-catalyzed cross-coupling of aryl iodides with terminal alkynes, the Castro ± Stephens ± Sonogashira reaction [5] using a palladium ± guanidinophosphane catalyst formed in situ, complies with these demands.Water-soluble palladium catalysts for CÀC cross-coupling usually employ sulfonated anionic triphenylphosphanes as ligands.[6] Under the basic reaction conditions required for Sonogashira reactions the proteins themselves carry a net negative charge as well, so that the catalytic process would have to overcome an electrostatic barrier. Experimental data indeed show that the catalytic activity of the cationic guanidinophosphanes 1 and 2, which we recently synthesized, is well enhanced.…”