SYNTHETIC AND QUANTUM-CHEMICAL EXPLORATION OF THE SELECTIVITY OF DONOR/ACCEPTOR-SUBSTITUTED METALLOCARBENOIDS Pubblico
Hansen, Jorn Hedloy (2010)
Abstract
Transient metallocarbenoids have become versatile intermediates for
organic synthesis.
Although a variety of applications have already been described, the
broad spectrum of
reactions displayed by these intermediates has led to an enormous
growth in research
efforts in later years. The donor/acceptor-substituted carbenoids,
derived from aryl- and
vinyldiazoacetates, are particularly stabilized and can effect
highly stereo- and
chemoselective transformations. In this work, factors controlling
the selectivity of these
species have been studied.
The rational syntheses of novel mixed-ligand dirhodium carboxylate
catalysts of well-
defined structure are described herein. The method can be used to
generate several unique
paddlewheel structures. A new class of chiral dirhodium
tetracarboxylate catalysts has
also been designed, that show considerable promise for asymmetric
induction in
carbenoid chemistry.
The selectivity of donor/acceptor-substituted rhodium carbenoids
has been studied by
Density Functional calculations. The calculations have demonstrated
why these
carbenoids are more selective than traditional carbenoid systems. A
new model for the
prediction of stereochemistry in intermolecular C-H insertions was
also developed from
these studies. The details of the mechanism of the combined C-H
activation/Cope
rearrangement have also been described, based on extensive studies
of the potential
energy surfaces.
The influence of metals, other than dirhodium complexes, on the
selectivity and
reactivity of donor/acceptor-substituted carbenoids has been
studied. It was found that a
new family of electron-deficient ruthenium(I) carbonyl carboxylates
and silver salts
greatly enhance vinylogous reactivity of their corresponding
vinylcarbenoid
intermediates. Heterobimetallic bismuth-rhodium carboxylate
complexes were also
shown to be effective catalysts for carbenoid transformations,
although they were much
less reactive than dirhodium catalysts. Comparative studies with
analogous dirhodium
complexes revealed that, axial coordination to the dirhodium
catalysts during the catalytic
cycle for carbenoid reactions, may greatly influence the
reactivity.
A convenient and practical method for selective cross-dimerization
of two diazo
compounds has been developed. A variety of fumarates are available
through this
chemistry. The selectivity of the reaction was shown to rely on the
preferred formation of
donor/acceptor-substituted carbenoids during the catalytic cycle.
Underlying control
elements that determine the feasibility of cross-dimerization
reactions were identified.
Table of Contents
Table of Contents
Chapter 1 Elements of Chiral Catalyst Design Based on the Rh(II)-Carboxylate Paddlewheel Scaffold 1
1.1 Introduction............................................................................................................ 1
1.2 Results and Discussion......................................................................................... 24
1.2.1 Mixed Ligand Dirhodium Carboxylates.......................................................... 24
1.2.2 Design of a Novel Family of Chiral Dirhodium Tetracarboxylates.................. 36
1.3 Conclusions............................................................................................................. 44
1.4 Experimental Section............................................................................................... 45
1.4.1 General Considerations.................................................................................... 45
1.5.2 Procedures and Characterization Data............................................................. 46
References..................................................................................................................... 59
Chapter 2 Density Functional Studies on the Selectivity of Donor/Acceptor-Substituted Rhodium Carbenoids 68
2.1 Introduction............................................................................................................. 68
2.2 Results And Discussion........................................................................................... 81
2.2.1 Selectivity of Rhodium Carbenoids................................................................. 81
2.2.2 Cyclopropenation Chemistry.......................................................................... 103
2.2.3 The Combined C-H Activation/Cope Rearrangement................................... 105
2.3 Conclusions........................................................................................................... 126
2.4 Experimental Section............................................................................................. 128
2.4.1 General Considerations.................................................................................. 128
2.4.2 Basis Sets and Pseudopotentials.................................................................... 129
2.4.3 Calculated Properties and Geometries........................................................... 131
2.4.4 Single Point Energy Calculations................................................................... 189
References................................................................................................................... 191
Chapter 3 Influence of Ru(I)- and Ag(I)-Catalysts on The Vinylogous versus Carbenoid Reactivity of Transient Metallovinylcarbenoids................................................................................................... 197
3.1 Introduction........................................................................................................... 197
3.2 Results And Discussion......................................................................................... 204
3.2.1 Electron-Deficient Ru(I) Carbonyl Carboxylates........................................... 204
3.2.2 Silver(I)-Catalyzed Reactions of Vinyldiazoacetates.................................... 210
3.3 Conclusions........................................................................................................... 230
3.4 Experimental Section............................................................................................. 231
3.4.1 General Considerations.................................................................................. 231
3.4.2 Procedures and Characterization Data........................................................... 232
3.4.3 General Computational Considerations.......................................................... 256
3.4.4 Calculated Structures and Properties............................................................. 257
3.4.5 Single Point Energy Calculations................................................................... 268
References........................................................................................................................269
Chapter 4 Bismuth-Rhodium Paddlewheel Carboxylates as Catalysts for Metallo-carbenoid Transformations 274
4.1 Introduction........................................................................................................... 274
4.2 Results And Discussion......................................................................................... 279
4.2.1 Catalytic Activity: Cyclopropanation Chemistry........................................... 279
4.2.2 Reactivity....................................................................................................... 282
4.2.3 Electronic Effects........................................................................................... 283
4.2.4 C-H Insertion Chemistry............................................................................... 286
4.2.5 Vinylogous Reactivity.................................................................................... 288
4.2.6 Density functional studies.............................................................................. 289
4.4 Conclusions........................................................................................................... 299
4.5 Experimental Section............................................................................................. 300
4.5.1 General Considerations for Synthetic Studies............................................... 300
4.5.2 Procedures and Characterization Data........................................................... 301
4.5.3 General Considerations for Computational Studies....................................... 308
4.5.4 Calculated Properties and Geometries........................................................... 312
4.5.5 Single Point Energy Calculations................................................................... 337
References....................................................................................................................... 338
Chapter 5 On The Rhodium(II)-Catalyzed Dimerization of Diazo Compounds......... 346
5.1 Introduction........................................................................................................... 346
5.2 Results And Discussion......................................................................................... 356
5.2.1 Synthetic Studies............................................................................................ 356
5.2.3 Mechanistic Studies........................................................................................ 363
5.3 Conclusions........................................................................................................... 376
5.4 Experimental Section............................................................................................. 377
5.4.1 General Synthetic Considerations.................................................................. 377
5.4.2 Procedures And Characterization Data.......................................................... 378
5.5.3 General Considerations for Computational Studies....................................... 394
5.5.4 Calculated Properties and Geometries........................................................... 395
References................................................................................................................... 411
Appendix ANMR Spectral Data for Representative Compounds...............................416
Appendix BX-Ray Crystallographic Data...................................................................422
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