No abstract

The Favorsky reaction of a wide range of aldehydes and ketones with alkynes has been implemented under mild conditions (5–20 °C). Using a Bu4NOH/H2O/DMSO catalytic system, propargylic alcohols are formed cleanly in 39–93 % (mostly 72–93 %) yields and with ca. 100 % selectivity. The method is suitable for aliphatic, aromatic, and heteroaromatic aldehydes and ketones, and for aliphatic, aromatic, and functionalized acetylenes. Thus, this represents the most general and efficient protocol to achieve the Favorsky reaction.

Scheme 1. Previous Works Scheme 2. KOBu t /DMSO-Catalyzed [3 + 2] Cycloaddition of Ketimine 1a to Acetylene 2a Letter pubs.acs.org/OrgLett

Acetylene reacts with methylaryl(hetaryl)ketones in the presence of 6.5 mol % KOH in DMSO to give diastereoselectively in single operationally functionalized cyclopentenes. This domino cyclization involving two molecules of acetylene and two molecules of ketone proceeds with the formation of four C-C bonds. The complementary assembly of the cyclopentenes with similar functionalities from acetylenes and 1,5-diketones has been developed.

A one‐pot transition metal‐free synthesis of propargylamines in good to excellent yield from ketone‐derived imines and aryl‐ and hetarylacetylenes in the presence of KOBut/DMSO superbase system (40 °C, 10 min) has been developed. The reaction involves a nucleophilic addition of acetylenic carbanions to the C=N bond, thus for the first time featuring the aza‐Favorsky reaction.