Z-Selective Synthesis of Vinyl Boronates through Fe-Catalyzed Alkyl Radical Addition.

Z-Selective synthesis of vinyl boronates is challenging. This work describes Fe-catalyzed addition of alkyl radicals, formed by the corresponding alkyl halides, to ethynyl ethynylboronic acid pinacol ester that gives rise to Z-vinyl boronates in high stereoselectivity. The method works best for tertiary and secondary alkyl iodides. The Z-vinyl boronate products are easily converted to other Z-alkenes by transformation of the boronate group. The method is applied for the formal total synthesis of a 5-HT2c receptor agonist.

Deoxygenative trifluoromethylthiolation of carboxylic acids.

Here we describe a deoxygenative trifluoromethylthiolation method that yields trifluoromethyl thioesters from readily available carboxylic acids. The method is built upon an "umpolung" strategy where triphenylphosphine is used to first activate an electrophilic trifluoromethylthiolating reagent and then serves as an oxygen acceptor for the deoxygenation. The method is mild, efficient, broad-scope, and tolerant. It can be applied for the late-stage functionalization of numerous natural products and drug molecules containing a carboxylic acid group. The trifluoromethyl thioesters can be converted into trifluoromethyl thioethers by Pd-catalyzed decarbonylation.