Dimethyl Sulfoxide → 2-Bromo-3-propoxy-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalene

Participants

Reaction Conditions

Reaction Steps

1.4 g of sodium hydride, 50% in mineral oil, were suspended in 50 ml of abs. dimethyl sulphoxide and treated dropwise while cooling with ice with 8.5 g of 2-bromo-3-hydroxy-5,5,8,8-tetra-methyl-5,6,7,8-tetrahydro-naphthalene dissolved in 60 ml of abs. dimethylformamide. The reaction mixture was stirred at 40° C. for ½ hour and subsequently a solution of 4.4 g of propyl bromide in 20 ml of dimethylformamide was added while cooling with ice. After stirring at room temperature for 20 hours the mixture was poured into ice-water, extracted with ethyl acetate and the crude product obtained after drying and evaporation of the solvent was filtered over a silica gel column (eluent hexane/ethyl acetate=9:1). 9.5 g of 2-bromo-3-propoxy-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalene were obtained as a brownish oil. This oil was dissolved in 100 ml of abs. tetrahydrofuran and treated dropwise at −78° C. with 40 ml of tert.butyllithium, 1.4 molar in pentane. After stirring at −78° C. for ½ hour 75 ml of abs. dimethylformamide were added dropwise and the mixture was stirred at room temperature for 1 hour. The pale beige suspension was poured into ice-water and extracted with ethyl acetate. After drying and evaporation of the organic phase the crude product was filtered over a silica gel column (eluent hexane/5% ether). There were obtained 6.6 g of 2-formyl-3-propoxy-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-naphthalene as a pale yellow oil which solidified upon cooling, melting point 51-52° C.

Provenance & Evidence