Specific Conjugate Addition to [Alpha],[Beta]-Acetylenic Ketones (Report‪)‬

INTRODUCTION When a synthetic method was developed that made 3,3,4,4-tetraethoxybut-1-yne (TEB) easily available in large quantities [1,2], a program was launched to explore the chemical potential of this highly functionalized molecule. Among the studies in progress is an investigation of the ability of [alpha],[beta]-unsaturated acetylenic ketones to react with a range of nucleophiles. So far, the study has focused on three groups of ketones. The simplest one consists of one compound only, viz. 1,1-diethoxybut-3-yn-2-one (1), which is obtained in good yield by exposing TEB to slightly acidic conditions [3]. The second group consists of [gamma]-hydroxylated [alpha],[beta]-unsaturated acetylenic ketones (2) (synthesized by TEB-acetylide coupling with a range of aldehydes followed by deketalization), whereas the third is comprised of a variety of 5-acyloxy-1,1-diethoxyalk-3-yn-2-ones (3) (prepared by TEB-acetylide coupling with a range of aldehydes, followed by esterification, and completed by deketalization) (Scheme 1) [4]. Regarding the nucleophiles the focus has so far been mostly on thiolates, alcohols, amines, and dialkyl cuprates, and the results presented here will therefore be limited to these nucleophilic species.