Professor Donaldson received his B.A. in 1977 from Wesleyan University and his Ph.D. degree in organometallic chemistry from Dartmouth College in 1981. He was a Postdoctoral Research Associate at Brandeis University (1981-82) and a Visiting Assistant Professor at Wesleyan (1982-83) before joining the faculty at Marquette University in August 1983. Professor Donaldson was awarded the Edward D. Simmons Award for Junior Faculty Excellence (1988), the Rev. John R. Raynor Faculty Award for Teaching Excellence (1995), and a Alexander von Humboldt Research Fellow at Philipps- Universitaet Marburg, Germany (1990-91).
Application of acyclic (pentadienyl)iron(1+) cations: The reaction of acyclic pentadienyl iron cations (1) with nucleophiles may proceed either at the terminal carbon atoms (path a) and/or at internal positions (path b). The regioselectivity of these reactions depend on the substitutents present on the pentadienyl ligand, the "spectator" ligands attached to iron, and the nature of the nucleophile (ie. heteroatom nucleophiles, or organolithiums, or stabilized carbon nucleophiles), and in certain cases, the nucleophile counterion. (Diene)iron products (2) produced by “path a” are stable, isolable species in which the iron serves as a protecting group for the diene against oxidation, reduction and cycloaddition reactions; decomplexation under oxidative conditions generates the free ligand. (Pentenediyl)iron products produced by “path b”, which bear an electron withdrawing group at C1 (3a) are also stable, isolable species, however decomplexation of these (pentenediyl)iron complexes, via an oxidatively induced-reductive elimination, gives vinylcyclopropanecarboxylates. Additionally, if an alkenyl nucleophile is used, the resultant divinylcyclopropanes may undergo Cope rearrangement to give cycloheptadienes. In contrast, (pentenediyl)iron complexes without an electron withdrawing group at C1 (3b) are unstable and undergo carbon monoxide insertion and reductive elimination to generate cyclohexenones. Thus, the acyclic (pentadienyl)iron(1+) cations serve as a versatile precursor to conjugated dienes, cycloheptadienes, vinylcyclopropanes and cyclohexenones.
We have utilized this reactivity to prepare a variety of natural and non-natural product targets as indicated in Scheme 2.
Generation of molecular complexity from simple hydrocarbons: The use of simple, relatively inexpensive hydrocarbons as starting materials for the synthesis of complex molecules relies on efficient methods for their oxidation, rearrangement and/or functionalization. We have utilized cyclohexadiene as a precursor for a stereochemically diverse spectrum of polyhydroxyaminocyclohexanes (aminocyclitols, Scheme 3). In addition, reaction of (cyclooctatetraene)iron (4) with a variety of electrophiles generates isolable (dienyl)iron cations (5a and b, Scheme 4).
Preparation of oxane containing natural products: A wide variety of naturally occurring targets contain either tetrahydropyran or dihydropyran ring fragments. Carbon-carbon bond formation can be effected by reaction of in situ generated oxycarbenium ions (6, Scheme 5) with neutral nucleophiles. We have utilized this methodology for the preparation of (+)-decarestrictine L, the C1-C8 and C17-C24 rings of ambruticin, the C3-C15 segment of the phorboxazoles, and model compounds for the relative stereochemical assignment of the C1-C10 segment of amphidinol 2.
1) “Generation of Molecular Complexity from Cyclooctatetraene Preparation of Optically Active Protected Aminocycloheptitols and Bicyclo[4.1.0]undecatriene”, M. F. El-Mansy, A. Sar, S. Lindeman and W. A. Donaldson, Chem. Eur.J. 2013, 19, 2330-2366.
2) “Generation of molecular complexity from cyclooctatetraene using dienyliron and olefin metathesis methodology”, M. F. El-Mansy, A. Sar, S. Chaudhury, N. J. Wallock and W. A. Donaldson, Org. Biomol. Chem. 2012, 10, 4844-4846. doi: 10.1039/c2ob25636c
3) “Reactivity of acyclic (pentadienyl)iron(1+) cations: Synthetic studies directed toward the frondosins”, D. W. Lee, R. K. Pandey, S. Lindeman and W. A. Donaldson, Org. Biomol. Chem. 2011, 9, 7742-7747. doi: 10.1039/C1OB05720K
5) “Denovo synthesis of polyhydroxy aminocyclohexanes”, A. Sar, S. Lindeman and
W. A. Donaldson, Org. Biomol. Chem. 2010, 3908-3917. doi: 10.1039/C004730A
6) “Synthetic studies directed toward guianolides: An organoiron route to the 5,7,5 tricyclic ring system”, J. R. Gone, N. J. Wallock, S. Lindeman and W. A. Donaldson, Tetrahedron Lett. 2009, 50, 1023-1025. doi:10.1016/j.tetlet.2008.12.051
7) “Synthetic studies directed toward amphidinol 2: Elucidation of the relative configuration of the C1-C10 fragment”, P. Kommana, S. W. Chung and W. A. Donaldson, Tetrahedron Lett. 2008, 49, 6209-6211. doi:10.1016/j.tetlet.2008.08.035
8) “Reactivity of (2-Alkenyl-3-pentene-1,5-diyl)iron Complexes: Preparation of Functionalized Vinylcyclopropanes and Cycloheptadienes”, R. K. Pandey, L. Wang, N. J. Wallock, S. Lindeman and W. A. Donaldson, J. Org. Chem. 2008, 73, 7236-7245. doi: 10.1021/jo801446q
9) “Synthesis of Cyclopropanes via Organoiron Methodology: Preparation of rac-Dysibetaine CPa”, T. A. Siddiquee, J. M. Lukesh, S. Lindeman and W. A. Donaldson, J. Org. Chem., 2007, 72, 9802-9803. doi: 10.1021/jo7020604
10) “Generation of Molecular Complexity from Cyclooctatetraene: Synthesis of a Protected 2-(3’-Carboxy-2’-benzoylcyclopentyl)glycine”, S. Chaudhury, S. Lindeman and W. A. Donaldson, Tetrahedron Lett., 2007, 48, 7849-7852. doi:10.1016/j.tetlet.2007.08.110
11) “Preparation, Characterization and Reactivity of (3-Methylpentadienyl)iron(1+) Cations”, S. Chaudhury, S. Li, D. W. Bennett, T. A. Siddiquee, D. T. Haworth and W. A. Donaldson, Organometallics, 2007, 26, 5295-5303. doi: 10.1021/om7006248
12) “Synthesis of Cyclopropanes via Organoiron Methodology: Stereoselective Preparation of Biscyclopropanes”, R. K. Pandey, S. Lindeman and W. A. Donaldson, Eur. J. Org. Chem. 2007, 3829-3831. doi: 10.1002/ejoc.200700431