(E)-4-chloro-2-methylbut-2-enal

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 11.8 g (0.1 mole) 2-methyl-4-chloro-2-butenal is dripped at ambient temperature into a solution of 10.4 g (0.13 mole) of potassium methylate in 60 ml of methanol and the whole is stirred for an hour. The product is worked up as described in Example 1. 10.5 g of 2-methyl-4,4-dimethoxybutanal is obtained by distillation at subatmospheric pressure. According to gas chromatographic and nmr analysis it has a purity of more than 98%. The yield is 72% of theory.

Conditions: temp:-20.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 5 ml of boron fluoride etherate were added to 1 liter of methylene chloride and the mixture was cooled to -20° C. A solution of 452 g (6.84 moles) of cyclopentadiene and 712 g (6.0 moles) of 3-formyl-crotyl chloride were added, whilst stirring, at a rate such that the reaction temperature did not rise above -10° C. The reaction mixture was then stirred for 3 hours at -10° C. To work up the reaction mixture, it was poured onto 1 kg of ice and neutralized with sodium carbonate solution, and the methylene chloride solution was washed neutral with water. After distilling off the solvent under reduced pressure (12 mm Hg/50° C.), 1,139 g of reaction product remained. A sample distillation showed that the yield was about 90% of theory. did not rise above -10° C The reaction mixture was then stirred for 3 hours at -10° C the methylene chloride solution was washed neutral with water After distilling off the solvent under reduced pressure (12 mm Hg/50° C.), 1,139 g of reaction product A sample distillation

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 11.8 g (0.1 mole) 2-methyl-4-chloro-2-butenal is dripped at ambient temperature into a solution of 10.4 g (0.13 mole) of potassium methylate in 60 ml of methanol and the whole is stirred for an hour. The product is worked up as described in Example 1. 10.5 g of 2-methyl-4,4-dimethoxybutanal is obtained by distillation at subatmospheric pressure. According to gas chromatographic and nmr analysis it has a purity of more than 98%. The yield is 72% of theory.