Decarboxylative Oxyacyloxylation of Propiolic Acids: Construction of Alkynyl-Containing α-Acyloxy Ketones

Abstract

Novel decarboxylative oxyacyloxylation of propiolic acids has been developed. This reaction provides an efficient access to alkynyl-containing α-acyloxy ketones from readily available starting materials and exhibits significant functional group tolerance. Furthermore, oxyacyloxylation of terminal alkynes and aliphatic propiolic acids was also developed. A possible reaction mechanism is proposed based on mechanistic studies.

Metal -free PhI(OAc)2-oxidized decarboxylation of propiolic acids towards synthesis of α-acetoxy ketones and insights into general decarboxylation with DFT calculations

“…To improve the yield of the decarboxylative acetoxylation, H 2 O utilization was tested and a slightly increased yield of 83% was observed when 2.5 equivalents of H 2 O was included (Table 1, entries [15][16][17]. Subsequently, the study was extended to testing the AcOH volume.…”

“…Initially, we selected phenylpropiolic acid 1a as the model substrate for reaction uncovering and treated with 3.0 equivalents of PhI(OAc) 2 , 2.0 equivalents of H 2 O and 1 milliliter of acetic acid in acetone at 80 °C for 3 h. Surprisingly, the desired 2-oxo-2-phenylethyl acetate 2a was obtained in 48% yield, along with alkynyl-containing α-acyloxy ketone 3a as a byproduct, which was the main product in the work by Chen 16 (Table 1, entry 1). Through investigations of other hypervalent iodine reagents such as bis(trifluoroacetoxy)iodobenzene (PIFA), PhIO and 1-hydroxy-1,2-benziodoxol-3(1 H )-one (ABX), we found that PhI(OAc) 2 (DIB) gave the best yield of 94% (see ESI†).…”

“…In the absence of PhI(OAc) 2 and under standard reaction conditions, phenylpropiolic acid was quite unreactive for the decarboxylation (Scheme 2g), suggesting perhaps that the decarboxylation was necessarily promoted by PhI(OAc) 2 . This decarboxylation process attracted our attention, 16,19 and we performed DFT calculations to describe the departure of carbon oxide, accompanied by energy barriers and the structure of the transition state (Fig. 1).…”

“…14 Meanwhile, the first intramolecular decarboxylative Heck-type reaction of 2-vinyl-phenyl oxamic acids mediated by hypervalent iodine( iii ) offered a variety of quinolones. 15 Li et al recently reported a decarboxylative oxyacyloxylation reaction of propiolic acids promoted by hypervalent iodine( iii ), 16 but the application of hypervalent iodines in the decarboxylation of carboxylic acids is still a focus of researchers.…”

(±)-((2S,5R)-5-(Acetoxymethyl)tetrahydrofuran-2-yl)methyl Benzoate

“…To this end, we planned the synthesis of a set of bis- The keen interest of synthetic organic chemists towards α-acyloxy ketones is demonstrated by the numerous methods developed to obtain these substances (see for example Refs. [20][21][22][23][24]). However, the synthesis and the chemistry of bis-α-acyloxy diketones such as 2 (Scheme 1) are largely unexplored.…”