Citronellal aldol reaction

Following this concept, a synthesis of hexahydrocannabinol 1 starts with the metallation of MOM-protected olivetol 5 (MOM = wethoxywethylether) ortho to both 0-alkyl groups with -butyllithium. The intermediate aldol 6 obtained by aldol reaction with citronellal 3 is deprotected and dehydrated when refluxed in methanol solution in the presence of /7-toluenesulfonic acid, and directly undergoes an intramolecular hetero Diels-Alder reaction to the target 1 on the expected pathway. 

Epoxyolefins. Epoxyolefins can be obtained in fair yield by addition of aldehydes in DMSO dropwise to the reagent. Polymers are also formed by aldol-type condensation. A mixture of unscparable diastereoisomeric epoxides is formed. The reaction of citronellal (1) to give 8,9-epoxy-2,6-dimethyl-2-nonene (2a, 2b) is formulated. 

Another interesting example of ort/zo-addition to phenol complexes is its reaction with aldehydes. In the presence of a weak base, the aldehyde undergoes an aldol condensation at C2 to give a rare example of a stable o-quinone methide complex. In Fig. 9 citronellal (34) is combined with phenol complex 20 to generate the quinone methide 35. Upon oxidative decomplexation a hetero-Diels-Al-der reaction occurs to form the benzochromene core 37 in 52% yield [48]. 

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