Figure 25.
(A) Site selective O–H insertion of 126 with Rh2(OAc)4. 4-bromophenyl-substituted diazo esters were found to give the best selectivity for mono O–H insertion. (B) Expansion of complex molecule substrate scope for site-selective O–H insertion. All compounds give one mono insertion product, with the exception of 147, which gives primarly diether 149. Note: numbers in parantheses represent %RSM. (C) Alteration of dirhodium catalyst perturbs the ratio of the two mono insertion products. Abbrev: HBPA: 5-hexynyl-(α-4-bromophenyl)acetate.172