1,3-Transposition of Allylic Alcohols Catalyzed by Methyltrioxorhenium

Abstract

Methyltrioxorhenium (MTO) catalyzes the 1,3-transposition of allylic alcohols to generate the more stable isomer at equilibrium. The direction of the equilibrium is largely decided by the nature of the OH group, i.e., whether it is primary, secondary, or tertiary. In the case of aliphatic allylic alcohols, tertiary is preferred to secondary which is preferred to primary. For aromatic allyl alcohols, the more conjugated isomer predominates largely at equilibrium. Oxygen-18 labeling showed that the OH groups of the parent and product are the same. The reaction is first order with respect to both allyl alcohol and MTO but strongly inhibited by traces of water. Theoretical calculations suggest the same results in the case of aliphatic allyl alcohols, although aromatic allyl alcohols do not follow the predictions. Studies of deuterium-labeled substrates show a large equilibrium isotope effect (K = 1.20 ± 0.02). For isomeric allyl alcohols differing in the position of deuterium only, the isomer with the deuterium at the sp3center predominates at equilibrium. The effect of conjugation from a phenyl group appears to be less important since calculations suggest that the phenyl group is forced out of plane of the allylic π system. Disciplines Chemistry CommentsReprinted (adapted) Methyltrioxorhenium (MTO) catalyzes the 1,3-transposition of allylic alcohols to generate the more stable isomer at equilibrium. The direction of the equilibrium is largely decided by the nature of the OH group, i.e., whether it is primary, secondary, or tertiary. In the case of aliphatic allylic alcohols, tertiary is preferred to secondary which is preferred to primary. For aromatic allyl alcohols, the more conjugated isomer predominates largely at equilibrium. Oxygen-18 labeling showed that the OH groups of the parent and product are the same. The reaction is first order with respect to both allyl alcohol and MTO but strongly inhibited by traces of water. Theoretical calculations suggest the same results in the case of aliphatic allyl alcohols, although aromatic allyl alcohols do not follow the predictions. Studies of deuterium-labeled substrates show a large equilibrium isotope effect (K ) 1.20 ( 0.02). For isomeric allyl alcohols differing in the position of deuterium only, the isomer with the deuterium at the sp 3 center predominates at equilibrium. The effect of conjugation from a phenyl group appears to be less important since calculations suggest that the phenyl group is forced out of plane of the allylic π system.

Catalytic selective oxidation of benzyl alcohols to aldehydes with rhenium complexes

“…Allylic, homoallylic and poly-unsaturated alcohols (2-propen-1-ol, 3-buten-1-ol, (2E)-3,7-dimethyl-2,6-octadien-1-ol (geraniol), (2Z)-3,7-dimethyl-2,6-octadien-1-ol (nerol) and (2E,6E)-3,7,11-trimethyl-2,6,10-dodecatrien-1-ol (farnesol)) show reactivity similar to the substituted benzyl alcohols, but no selectivity (isomerisation and oxidation to aldehydes, acids, esters). This result is consistent with earlier reports that 5 in the presence of 4-methylbenzenesulfonic acid in CH 2 Cl 2 [30][31] or MeReO 3 (MTO) by itself [32] catalyse the metathesis and dehydration of allylic alcohols.…”

Rhenium‐Catalyzed Deoxydehydration of Diols and Polyols

“…[45] The extrusion was concluded to be the rate-limiting step. The observation that cis-2-butene-1,4diol isomerized to 3-butene-1,2-diol was corroborated in 1998 by Espenson and Gordon, [57] who investigated the CH 3 ReO 3catalyzed isomerization (or 1,3-transposition, see Scheme 9) of allylic alcohols, and in 2013 by Shiramizu and Toste, who expanded the scope of the isomerization to diols, in which the hydroxyl groups were separated by two carbon-carbon double bonds (e.g., 2,4-hexadiene-1,6-diol). The observation that cis-2-butene-1,4diol isomerized to 3-butene-1,2-diol was corroborated in 1998 by Espenson and Gordon, [57] who investigated the CH 3 ReO 3catalyzed isomerization (or 1,3-transposition, see Scheme 9) of allylic alcohols, and in 2013 by Shiramizu and Toste, who expanded the scope of the isomerization to diols, in which the hydroxyl groups were separated by two carbon-carbon double bonds (e.g., 2,4-hexadiene-1,6-diol).…”

Methyltrioxorhenium and its applications in olefin oxidation, metathesis and aldehyde olefination

“…With added acid the triol is obtained. The 1,3-transpositioning of allylic alcohols, also catalyzed by MTO, however, is strongly inhibited by the presence of traces of water [102]. This reaction does not require the presence of peroxides or peroxo complexes.…”