Preparation of δ-Chloro-α-allenyl Ketones by Acylation of 3-Buten-1-ynes

Abstract

AlCl(3)-mediated acylation of 3-buten-1-yne derivatives with acyl chlorides yields a mixture of 5-chloro-2,3-pentadienones and 3-chloro-2,4-pentadienones. The proportion of allenyl ketones vs conjugated dienic ketones depends on the substitution pattern of the starting enyne. Acylation of 5-acetoxy-3-buten-1-ynes leads to the corresponding allenyl ketones (6-acetoxy-5-chloro-2,3-pentadienones).

Regioselective Cationic 1,2- and 1,4-Additions Forming Carbon−Carbon Bonds to Methyl Santalbate, a Conjugated Enyne

“…[7] Our results show that, in the case of the conjugated enyne 1, the milder Lewis acid Me 2 AlCl has to be used, because in the presence of EtAlCl 2 a complex mixture of products was obtained. The mechanism and the regioselectivity of the acylation reaction have been discussed by Santelli-Rouvier et al [5] Fatty acid derivatives with an allenic system are known to have interesting properties, [11] and in special cases they have been used as substrates in the synthesis of new fatty compounds; one example is as a C 18 keto allenic ester for the synthesis of pyrazole ester derivatives. [12] In analogy to FriedelϪCrafts alkylations of alkenes, [8] the corresponding reaction of 1 was carried out with isopropyl chloroformate and ethylaluminium sesquichloride (Et 3-Al 2 Cl 3 ) (Scheme 2).…”

“…δ-Chloro-α-allenyl ketones have been obtained regioselectively from AlCl 3 -mediated acylation reactions of 3-buten-1-ynes with acyl chlorides. [4,5] Recently, our interest has been focused on carbonϪcarbon bond-forming addition reactions to unsaturated fatty compounds, to obtain new branched and/or chain-elongated fatty compounds with possibly interesting properties. [6] Up to now, we have carried out electrophilic additions such as FriedelϪCrafts acylations, [7] FriedelϪCrafts alkylations [8] and ene additions of formaldehyde [9] to mono-unsaturated fatty acids.…”