Abstract
A one-pot iron-catalyzed conversion of allylic alcohols to α-methyl ketones has been developed. This isomerization–methylation strategy utilized a (cyclopentadienone)iron(0) carbonyl complex as precatalyst and methanol as the C1 source. A diverse range of allylic alcohols undergoes isomerization–methylation to form α-methyl ketones in good isolated yields (up to 84% isolated yield).
Highlights
Motherwell and co-workers have reported the only direct one-pot conversion of secondary allylic alcohols to α-methyl ketones to date (Scheme 1B).[10]
Despite the benefits of a one-pot procedure, the disadvantages of this method include the use of a precious metal catalyst, a pyrophoric base, and superstoichiometric quantities of a toxic methylating agent
Control experiments confirmed that no product was formed in the absence of iron precatalyst 2 or K2CO3
Summary
Motherwell and co-workers have reported the only direct one-pot conversion of secondary allylic alcohols to α-methyl ketones to date (Scheme 1B).[10]. In an effort to address these drawbacks, we have utilized a (cyclopentadienone)iron(0) carbonyl complex (2 mol %)[11] for the one-pot isomerization−methylation of allylic alcohols to α-methyl ketones (Scheme 1C). The isomerization−methylation of 1-phenylprop-2-en-1-ol 1 was selected as the model system for optimization studies (Table 1).[12] It was determined that (cyclopentadienone)iron(0) carbonyl complex 2 (2 mol %),[13] Me3NO (4 mol %),[14] and K2CO3 (2 equiv) in MeOH ([1] = 0.5 M) at 130 °C for 24 h, facilitated the isomerization−methylation of 1, which gave product 3 in 88% NMR yield and 76% isolated yield (entry 1).
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