Magnesium-promoted reductive acylation of aromatic conjugated ynones accompanying with transposition of the triple bond

Conjugated Ynones in Organic Synthesis

“…Thus, both substrates 71 and an acyl chloride react with Mg in DMF to give mainly conjugated enyne 718 via intermediates I− IV resulting from an electron transfer and reaction of the generated anion with the electrophile (Scheme 317). 527 When ynones 71 were allowed to react with malononitrile in toluene at 120 °C, polysubstituted anilines 719 were isolated (Scheme 318). The reaction starts with a condensation of both reagents to give intermediate 720, which suffers a Michael-type addition affording 721, that reacts with a third molecule of the dinitrile to yield 722, a direct precursor of the final product 719. new opportunities to prepare a variety of heterocyclic compounds with control of the substitution pattern.…”

Synthesis of 4-(Trifluoromethyl)cyclopentenones and 2-(Trifluoromethyl)furans by Reductive Trifluoroacetylation of Ynones

“…In our recent work, magnesium-promoted reductive acylation of aromatic ynones in the presence of acyl chlorides afforded the corresponding enyne derivatives, and the triple bond of aromatic ynones was transposed to the neighboring position via the allene intermediate formation and subsequent decomposition in situ (Scheme , previous work). In connection with our interest in organofluorine chemistry, we supposed that the use of ethyl trifluoroacetate ( 2a ) in reactions with ynone 1 might give a simple β-trifluoroacetylated product, similar to our previous research.…”

“…In addition, this synthesis of furan derivatives could be applied to ynones with an aromatic ring such as 1-naphthyl or 2-thienyl group ( 10l and 10m ). On the basis of our previous reports ,,, and investigation on reduction potential of ynones 1 , 7 , chlorotrimethylsilane, and ethyl trifluoroacetate 2a , plausible reaction mechanisms for the trifluoroacetylation and deacetalization were proposed in Scheme . First, a single-electron transfer from magnesium metal to aromatic ynone 1a will give an anion radical species, which is attacked by a chlorotrimethylsilane and then obtains the second electron to form an intermediate A .…”