Catalytic Allylic Oxidation to Generate Vinylogous Acyl Sulfonates from

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Cite This: Org. Lett. XXXX, XXX, XXX−XXX

Catalytic Allylic Oxidation to Generate Vinylogous Acyl Sulfonates from Vinyl Sulfonates James K. Tucker and Matthew D. Shair* Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States

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ABSTRACT: Regioselective formation of vinylogous acyl sulfonates was accomplished via the allylic oxidation of the corresponding vinyl sulfonates. The reaction progressed through the agency of catalytic iron(III) chloride catalysis with tert-Butyl hydroperoxide (TBHP) as the stoichiometric oxidant. Tolerance of other functional groups, including some other allylic and benzylic sites, was observed. Table 1. Experiments Concerning Catalyst Discoverya

V

inylogous acyl sulfonates are versatile intermediates for organic synthesis, undergoing a variety of coupling and fragmentation processes.1 These substrates typically originate from treatment of the corresponding 1,3-dicarbonyl with a weak base and sulfonate electrophile (Figure 1A). In the case

Figure 1. Proposed utility of an oxidative approach to vinylogous acyl sulfonates.

entry

solvent

cat.

NMR yield of 2a (%)

1 2 3 4 5 6 7 8 9b 10c 11 12 13d 14 15

ACN ACN ACN ACN ACN ACN ACN Acetone ACN ACN ACN ACN ACN PhH EtOAc

Rh2cap4 Pd(OH)2/C Na2CrO7 Cul Cu(OAc)2 Fe(acac)3 FeCl3 FeCl3 FeCl3 FeCl3 FeCl2 none FeCl3 FeCl3 FeCl3

63 21 70 57 67 35 93 89 55 63 73 ca. 10