ORGANIC
LETTERS
2012
Vol. 14, No. 14
3796–3799
Iron-Catalyzed Alkylations of Aryl
Sulfamates and Carbamates
Amanda L. Silberstein, Stephen D. Ramgren, and Neil K. Garg*
Department of Chemistry and Biochemistry, University of California, Los Angeles,
California 90095-1569, United States
Received June 19, 2012
ABSTRACT
The alkylation of aryl sulfamates and carbamates using iron catalysis is reported. The method constructs sp2Àsp3 carbonÀcarbon bonds and
provides synthetically useful yields across a range of substrates (>35 examples). The directing group ability of sulfamates and carbamates,
accompanied by their low reactivity toward conventional cross-couplings, renders these substrates useful for the synthesis of polyfunctionalized
arenes.
As one of the most abundant, inexpensive, and nontoxic
elements on earth, iron hasbeen hailedasanideal metal for
the development of catalytic transformations.1 Various
Fe-based methods to promote CÀC bond formation have
been reported since the seminal publications of Kharasch2
and Kochi,3 with many key advances being described in
the past decade.1 One especially promising area is iron-
is testament to the promise of this developing field of
research.6
With the aim of discovering iron-promoted reactions for
use in synthesis, we explored iron-catalyzed reactions of
aryl sulfamate and carbamate substrates. These substrates
have recently garnered significant attention in cross-
coupling reactions because of their ease of preparation,
pronounced stability to a variety of reaction conditions,
including conventional transition metal catalysis, and their
directing group ability for arene functionalization.7,8
Sulfamates and carbamates have primarily been used in
catalyzed cross-coupling reactions of aryl electrophiles,4,5
4a,b
€
largely pioneered by Furstner,
which nicely comple-
ments the most commonly used Pd- and Ni-based meth-
ods for forging CÀC bonds. The use of iron-mediated
coupling reactions in natural product and drug synthesis
€
(6) (a) Furstner, A.; Leitner, A. Angew. Chem., Int. Ed. 2003, 42, 308.
€
(b) Seidel, G.; Laurich, D.; Furstner, A. J. Org. Chem. 2004, 69, 3950. (c)
€
(1) (a) Sherry, B. D.; Furstner, A. Acc. Chem. Res. 2008, 41, 1500. (b)
€
Scheiper, B.; Glorius, F.; Leitner, A.; Furstner, A. Proc. Natl. Acad. Sci.
€
€
Furstner, A. Angew. Chem., Int. Ed. 2009, 48, 1364. (c) Furstner, A.;
Martin, R. Chem. Lett. 2005, 34, 624. (d) Czaplik, W. M.; Mayer, M.;
Cvengros, J.; Jacobi von Wangelin, A. ChemSusChem 2009, 2, 396. (e)
Ritter, S. K. Chem. Eng. News 2008, 86, 53.
(2) Kharasch, M. S.; Fields, E. K. J. Am. Chem. Soc. 1941, 63, 2316.
(3) (a) Tamura, M.; Kochi, J. K. J. Am. Chem. Soc. 1971, 93, 1487. (b)
Smith, R. S.; Kochi, J. K. J. Org. Chem. 1976, 41, 502.
U.S.A. 2004, 101, 11960.
(7) (a) Sengupta, S.; Leite, M.; Raslan, D. S.; Quesnelle, C.; Snieckus,
V. J. Org. Chem. 1992, 57, 4066. (b) Dallaire, C.; Kolber, I.; Gingras, M.
Org. Synth. 2002, 78, 42. (c) Macklin, T. K.; Snieckus, V. Org. Lett. 2005,
7, 2519. (d) When, P. M.; Du Bois, J. Org. Lett. 2005, 7, 4685. (e)
Quasdorf, K. W.; Riener, M.; Petrova, K. V.; Garg, N. K. J. Am. Chem.
Soc. 2009, 131, 17748. (f) Antoft-Finch, A.; Blackburn, T.; Snieckus, V.
J. Am. Chem. Soc. 2009, 131, 17750. (g) Quasdorf, K. W.; Antoft-Finch,
A.; Liu, P.; Silberstein, A. L.; Komaromi, A.; Blackburn, T.; Ramgren,
S. D.; Houk, K. N.; Snieckus, V.; Garg, N. K. J. Am. Chem. Soc. 2011,
133, 6352. (h) Xu, L.; Li, B.-J.; Wu, Z.-H.; Lu, X.-Y.; Guan, B.-T.;
Wang, B.-Q.; Zhao, K.-Q.; Shi, Z.-J. Org. Lett. 2010, 12, 884. (i)
Baghbanzadeh, M.; Pilger, C.; Kappe, C. O. J. Org. Chem. 2011, 76,
1507.
(8) For reviews, see: (a) Knappke, C. E. I.; Jacobi von Wangelin, A.
Angew. Chem., Int. Ed. 2010, 49, 3568. (b) Yu, D.-G.; Li, B.-J.; Shi, Z.-J.
Acc. Chem. Res. 2010, 43, 1486. (c) Li, B.-J.; Yu, D.-G.; Sun, C.-L.; Shi,
Z.-J. Chem.;Eur. J. 2011, 17, 1728. (d) Rosen, B. M.; Quasdorf, K. W.;
Wilson, D. A.; Zhang, B.; Resmerita, A.-M.; Garg, N. K.; Percec, V.
Chem. Rev. 2011, 111, 1346.
(4) For the iron-catalyzed alkylation of aryl halides, tosylates, and
€
triflates, see: (a) Furstner, A.; Leitner, A. Angew. Chem., Int. Ed. 2002,
€
ꢀ
41, 609. (b) Furstner, A.; Leitner, A.; Mendez, M.; Krause, H. J. Am.
€
Chem. Soc. 2002, 124, 13856. (c) Furstner, A.; Martin, R.; Krause, H.;
€
Gunter, S.; Goddard, R.; Lehmann, C. W. J. Am. Chem. Soc. 2008, 130,
8773. For the iron-catalyzed alkylation of heteroaromatic sulfonates
and phosphates, see: (d) Gøgsig, T. M.; Lindhardt, A. T.; Skrydstrup, T.
Org. Lett. 2009, 11, 4886. (e) For a relevant mechanistic study, see:
Kleimark, J.; Larsson, P.-F.; Emamy, P.; Hedstrom, A.; Norrby, P.-O.
Adv. Synth. Catal. 2012, 354, 448.
(5) For the related iron-catalyzed alkylation of styrenyl or electron-
deficient vinyl pivalates, see: Li, B.-J.; Xu, L.; Wu, Z.-H.; Guan, B.-T.;
Sun, C.-L.; Wang, B.-Q.; Shi, Z.-J. J. Am. Chem. Soc. 2009, 131, 14656.
€
r
10.1021/ol301681z
Published on Web 07/03/2012
2012 American Chemical Society