Allylic hydroxymethylation of cyclohexene and cyclooctene was achieved by metallation with trimethylsilylmethylpotassium followed by the reaction with formaldehyde, 1-Methylcycloalkenes were transformed into 2-methylenecycloalkane-1-methanols by the reaction of formaldehyde with allylic diethylboranes derived from these olefins via metallation-transmetallation. Conjugated cycloalkenecarboxaldehydes