AUTOXIDATION OF LIMONENE, ALPHA-PINENE AND BETA-PINENE BY DIOXYGEN CATALYZED BY CO(OAC)(2) BROMIDE/

It has been shown that NaBr addition to Co(OAc)(2) increases conversio ns in autoxidations, by dioxygen, of limonene (1), alpha-pinene (2) an d beta-pinene (3). Best selectivities towards allylic oxygenated produ cts were achieved with an optimum ratio [Co(OAc)(2)]/[NaBr] = 1, while keeping [Co(OAc)(2)] = 0.15 M. Using this system selectivities of 24. 1, 11.4, 14.8 and 20.6% were obtained, respectively for carvone (4), t rans-carveol (7a), trans- and cis-carvoyl acetate (9a and 9b) and 4-ac etoxy-p-mentha-1,8-diene (13) from limonene (1). Autoxidation of alpha -pinene (2) showed selectivities of 10.2, 19.5 and 29.5% for myrtanal (6), verbenone (5) and trans-verbenyl acetate (17a), respectively. Ver y good selectivities, 19 and 15.4%, were observed for terpinyl acetate (27) and myrtanal (6) from autoxidation of beta-pinene (3). Substitut ion of Co(II) by Mn(II) up to 30% M had no effect on conversions. Howe ver, this substitution (20-30% M) shifted selectivity significantly to wards alcohols and acetates, yielding selectivities of 20 and 18% for trans-carveol (7a) and trans- and cis-carvoyl acetate (9a and 9b) from limonene (1); 48% for verbenyl acetate (17a) from alpha-pinene (2) an d 16-18% for trans-pinocarveol (16) from beta-pinene (3). It was concl uded that, in this case, Mn(II) exercises a selectivity tuning effect.