Alkynyl halides are reduced by chromium(II) chloride in DMF to give unisolable alkynylchromium compounds which add selectively to an aldehyde moiety without affecting the coexisting ketone group of the substrate.
The synthesis of complex C-glycoconjugates is presented here using a key directed nickel-catalyzed C−H alkynylation step. Thanks to a bidentate amidoquinoline-type directing group, the insertion of diverse alkynyl moieties onto the pseudo-anomeric position of glycal substrates was performed on ten examples in moderate to good yields. These platforms were used as starting substrates in a click reaction
It was demonstrated that alkynyl halides could serve as a source of Br+ and acetylide ions in the same transformation. This allowed for the efficient one-step preparation of alkynyl epoxides, important organic building blocks, from readily available starting materials.
Palladium-Catalyzed Regioselective Alkynylation of Pyrroles and Azoles under Mild Conditions: Application to the Synthesis of a Dopamine D-4 Receptor Agonist
作者:Etienne Brachet、Philippe Belmont
DOI:10.1021/acs.joc.5b01093
日期:2015.8.7
A mild and general method for the direct alkynylation of azoles such as pyrrole, indole, and 7-azaindole is described here. Using a simple catalytic system such as Pd(OAc)(2) (2.5 mol %), P(tBu)(2)Me center dot HBF4 (5 mol %), and NaOAc (2 equiv) allowed the regioselective introduction of various alkynyl residues at the C-2 position of pyrroles. Interestingly, C-2 alkynylation was also observed on C-3-substituted indoles, whereas classical C-3 alkynylation was obtained on selected unsubstituted indoles and 7-azaindole. Our methodology has been illustrated by the efficient synthesis of a potential schizophrenia drug (dopamine D-4 inhibitor).