6-Octenal, 3,7-dimethyl-, (3R)- → (3r)-3,7-Dimethyloctanal

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A 3 L indented flask equipped with a mechanical stirrer and a H2 inlet was charged with 205.7 g (1.333 mol) of (R)-citronellal in 7.4L of ethyl acetate. The flask was flushed with 0.1 cu. ft. of H2 and 0.50 g (2.0 mmol) of platinum oxide were added. The reaction was stirred under a slight over-pressure of H2 at ambient temperature for 124 hours. During this time, due to relatively rapid deactivation of the catalyst, an additional 3.50 g (143 mmol.) of platinum oxide had to be added in 5 portions (0.5 g at 3.5 hours, 0.5 g at 22.5 hours, 1.0 g at 96.5 hours and 0.5 g at 121 hours). The course of the hydrogenation was monitored by GC analysis. After 124 hours, GC indicated the hydrogenation to be almost complete with 1.4% of starting material remaining. A total of 1.133 cu. ft. of hydrogen (theoretically 1.166 cu. ft.) had been consumed. The catalyst was removed by filtration through a pad of Celite (diatomaceous earth). The clear filtrate was combined with the filtrate from a previously run, analogous reduction of 10.0 g (64.8 mmol) of (R)-citronellal and concentrated on the rotovapor. Vacuum distillation of the obtained pale yellow liquid through a 30 cm Goodloe column afforded the (R)-3,7-dimethyloctanal in following fractions:

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