3-Methoxybenzyl alcohol → 5-Hydroxy-1,3-dihydro-2-benzofuran-1-one
Reaction equation
COC1C=C(C=CC=1)CO.C[O:12][C:13]1[CH:14]=[C:15]2[C:20](=[CH:21][CH:22]=1)[C:18](=[O:19])[O:17][CH2:16]2.COC1C=CC=C2C=1C(=O)OC2>>[OH:12][C:13]1[CH:14]=[C:15]2[C:20](=[CH:21][CH:22]=1)[C:18](=[O:19])[O:17][CH2:16]2Participants
4
Procedure
The reactions are also highly stereo- and regiospecific. Thus, thallation-carbonylation of cis- and trans-2-phenylcyclohexanoles (examples 7 and 8) provide exclusively the cis and trans fused tricyclic lactones respectively. Substituents on the aromatic ring are also observed to effect a very pronounced directive effect. For example, thallation-carbonylation of m-methoxybenzyl alcohol affords the 5-methoxyphthalide in 89% yield and only a trace of the 7-methoxyphthalide (example 4). Similarly, m-hydroxybenzyl alcohol affords a 95% isolated yield of pure 5-hydroxyphthalide (example 5).