Iodination of activated 1-hetero-1,3-dienes

4,4-Dialkoxybutan-2-ones as Synthons

“…Bleaching of a support by treatment with dialkoxybutanones 4 (R = Me, Et) in the presence of quaternary ammonium salts was covered by patent [68]. Gerus et al [69] and Campos et al [70] described halogenation of dialkoxybutanones 4 (R = Me, Et) as a synthetic route to polyhalogenated a-chloro-b-alkoxyvinyl ketones. Dialkoxybutanone 4a was used to obtain methyl b-(1-benzotriazolyl)vinyl ketone in which the benzotriazolyl group is readily replaced by morpholine, 2-nitropropane, and phenylbutyronitrile [71].…”

“…Darzens reaction of halogenated carboxylic acid esters with acetal 4a occurs at the carbonyl group of the latter to give ester 64 which undergoes intramolecular cyclization to furan derivative 66 through intermediate 65; the subsequent hydrolysis of ester 67 and decarb-MARETINA oxylation of acid 68 yield 3-methylfuran (69) [6, 15, 23] (Scheme 23). Acetal 4a reacts with 2-pyridylmethyllithium(70) to give alcohol 71 whose cyclization leads to 3-methylquinolizinium salt 72[6,17].…”

A General Method for the Highly Regioselective Introduction of Substituents into the 3-Position of 5-Unsubstituted 4-O-Alkyl Tetronates

“…To the best of our knowledge, to date there is only one report in the literature concerning the iodination of 4-O-alkyl tetronates: Campos et al described the reaction of compound 6a with bis(pyridine)iodonium(I) tetrafluoroborate (IPy 2 BF 4 ) in the presence of two equivalents of triflic acid to give iodide 7a in a 54% yield. 12 We found that simple treatment of 4-O-alkyl tetronates with excess iodine (4.0 equiv) and 1.0 equivalents of pyridine in DMF at room temperature is a much cheaper and even more efficient alternative. In this way 3iodo tetronates 7a and 7b were obtained in 86% and 80% yield, respectively, from the corresponding 3-unsubstituted tetronates 6.…”