Metal-Free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

Abstract

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups and scaffolds. Traditional methods for the preparation of ynones are associated with drawbacks including harsh conditions, multiple purification steps, and the presence of unwanted byproducts. An alternative method for the straightforward preparation of ynones from acyl chlorides and potassium alkynyltrifluoroborate salts is described herein. The adoption of organotrifluoroborate salts as an alternative to organometallic reagents for the formation of new carbon-carbon bonds has a number of advantages. Potassium organotrifluoroborate salts are shelf stable, have good functional group tolerance, low toxicity, and a wide variety are straightforward to prepare. The title reaction proceeds rapidly at ambient temperature in the presence of a Lewis acid without the exclusion of air and moisture. Fair to excellent yields may be obtained via reaction of various aryl and alkyl acid chlorides with alkynyltrifluoroborate salts in the presence of boron trichloride. Video LinkThe video component of this article can be found at

Metal-free methodology for the preparation of sterically hindered alkynoylphenols and its application to the synthesis of flavones and aurones

“…Compound 3 could be converted to the desired ynone intermediate (Scheme 3). 28 Unfortunately, conditions for the conversion of 2-3 resulted in partial decomposition making isolation of clean product a challenge. Additionally, this method is not ideal as a result of the number of steps required for the preparation of acyl chloride.…”

“…27 Previously, we have developed a straightforward procedure for the preparation of ynones from acyl chlorides and potassium alkynyltrifluoroborate salts (Scheme 2). 28 This convenient, one-pot reaction proceeds rapidly in the presence of boron trichloride without exclusion of air or moisture. Furthermore, alkynyltrifluoroborate salts can be easily prepared from terminal alkynes according to the published procedure.…”

Brønsted Acid-Catalyzed Direct Substitution of 2-Ethoxytetrahydrofuran with Trifluoroborate Salts

“…Unless otherwise noted, all reagents were obtained from Sigma-Aldrich (Oakville, ON, Canada or Milwaukee, WI, USA) and used without further purification. Potassium trifluoroborate salts were synthesized according to published procedures [4,5,16,50,51]. Reaction progress was monitored via thin layer chromatography (TLC) on silica gel (60 Å) with visualization using ultraviolet light (254 nm) and by staining with phosphomolybdic acid (PMA).…”

“…Potassium alkynyltrifluoroborate salts were prepared according to known procedures [4,5,16,51]. To a solution of the indicated terminal alkyne (1.0 equiv.)…”

Palladium anchored on amine-functionalized K10 as an efficient, heterogeneous and reusable catalyst for carbonylative Sonogashira reaction

“…Furthermore, the transition metal catalyzed cross coupling of acid chlorides with terminal alkynes is a common route toward alkynyl ketones [4]. Recently, transition metal free Lewis acid catalyzed reaction of alkynyltrifluoroborate salts with acid chloride has been reported for the synthesis of alkynyl ketones [5]. Tang et al have reported the synthesis of alkynyl ketones using Pd(OAc) 2 /bis[ (2-diphenylphosphino) phenyl] ether catalyst and tert-butyl isocyanide as a carbonylating reagent [6].…”