C O M M U N I C A T I O N S
Table 2. Substrate Scope for the Palladium-Catalyzed
Carbonylation of Aryl Sulfonates at Atmospheric CO Pressure
With regard to the alcohol the reaction was general with a variety
of primary alcohols and a secondary alcohol. The synthesis of esters
derived from lighter alcohols was limited by the boiling point of
the alcohol. Ethyl esters could be synthesized by running the
reactions at 80 °C. Carbonylation of modestly activated tosylates
and mesylates occurred at this temperature, and their ethyl esters
were obtained in good yield (entries 9 and 14); for substrates where
the aryl group was unactivated the more reactive p-fluorobenzene
sulfonate was employed to allow complete conversion to product
(entries 15 and 16).
In summary we have developed a mild and general procedure
for the carbonylation of aryl tosylates and mesylates at atmospheric
pressure of carbon monoxide and relatively low temperatures using
commercially available, air stable dccp•2HBF4 as the supporting
ligand.
Acknowledgment. Generous financial support from the MIT-
Singapore Alliance is gratefully acknowledged. We are indebted
to Merck, Amgen, and Boehringer-Ingelheim for unrestricted
support. We are also grateful to Nippon Chemical Co. for providing
ligand 1 and to BASF for a donation of palladium acetate.
Supporting Information Available: Experimental procedures and
spectral data for all new compounds. This material is available free of
References
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(9) Available from Nippon Chemical Co. (catalogue no. 103099-52-1).
(10) See Supporting Information for details of butoxyesterification of 4-t-
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(11) Substrates with certain electron-withdrawing groups (e.g., 3-cyanophenyl
methanesulfonate) were transformed into mixtures of butyl ether and ester
when the reaction was carried out in DMSO. Ether formation occurred
without ligand and Pd in DMSO presumably via a base-mediated sulfonyl
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was completely suppressed when the reaction was conducted in toluene
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a Isolated yields (average of two runs). b Reaction was performed with
5% (Pd(OAc)2 and 6% 1 for 22h. c Reaction proceeded to 88% conversion
(GC analysis). d Reaction was performed with 10 equiv EtOH. e Reaction
was performed with 4% Pd(OAc)2 and 4.4% 1. f Reaction was performed
with 5 equiv of EtOH for 20 h. g Concentration: 0.67 M toluene.
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