Attempted synthesis of a 3-pyranone from 3,3,4,4-tetraethoxybut-1-yne

The starting material for this project was the highly functionalised compound 3,3,4,4-tetratethoxybut-1-yne (TEB). One of the compounds that can be synthesised from TEB is 1,1-diethoxy-3-(1,3-dithian-2-yl)propan-2-ol (β-hydroxydithiane), which is used as the starting material in this investigation. TEB and β-hydroxydithiane have previously been synthesised in good yields using various reaction routes. The addition of benzaldehyde to β-hydroxydithiane furnished the corresponding 5,5-diethoxy-1-phenyl-2,2-(propyl-1,3-disulfanyl)pentane-1,4-diol in a very good yield, using reaction conditions that previously has only been attempted on a smaller scale. The subsequent deprotection of the dithiane moiety in 5,5-diethoxy-1-phenyl-2,2-(propyl-1,3-disulfanyl)pentane-1,4-diol gave only a poor yield of 5,5-diethoxy-1,4-dihydroxy-1-phenylpent-2-one. The cyclization attempt of 5,5-diethoxy-1-phenyl-2,2-(propyl-1,3-disulfanyl)pentane-1,4-diol was however more successful, and furnished 8-oxa-7-phenyl-1,5-dithiaspiro[5.5]undecane-9,10-diol acetonide as the major product