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of the metal into the allenyne leading to a metallocycle. The energy difference between the transition states in this step is responsible for the double bond selectivity in the respective reaction. In the Rh(I)-catalyzed reaction, the transition state leading to a [6,5]-fused metallocycle is better accommodated by the square-planar Rh(I)-center, compared to the transition state leading to a [5,5]-metallocycle. In contrast, the transition state leading to a [5,5]-metallocycle is preferred by the distorted trigonal-bipyramidal molybdenum center in the Mo-mediated reaction. These calculations show that the double bond selectivity is result of the geometry constraints imposed by the metal center in the oxidative addition step of the reaction. We are speculating that the presence of a diphosphine ligand (dppb) on the Rh(I)-center results in a transition-state geometry that can better accommodate the formation of the [5,5]-metallocycle. Further studies at supporting this hypothesis will be forthcoming. 138
Conclusions In summary, we have demonstrated a diversity-oriented synthetic strategy based on transition metal-catalyzed and mediated reactions of allenes (Scheme 4.56). We have gained access to a number of structurally and functionally unique products in a relatively short number of synthetic steps. Amino-acid derived allenes accessed via Claisen rearrangement were used as pivotal synthetic intermediates. The Rh(I)-catalyzed allenic Alder-ene reaction of allenynes proceeds in excellent yield affording cross conjugated trienes. These compounds were studied in sequential cycloaddition reactions, gaining access to complex polycyclic skeletons. Furthermore, a novel cycloisomerization of propiolamides was developed affording δ-lactams. Modified catalytic conditions were developed to allow the synthesis of 4-alkylidene cyclopentenones. While studying the Mo-mediated cyclocarbonylation reaction of amino-ester tethered allenynes, a novel stereocontrol element was uncovered based on the amino-acid side chain. The knowledge gained from these studies was used to design and synthesize a novel class of tricyclic pyrroles via a Stetter/Paal-Knorr reaction sequence. By modifying the substrate to include an alkene instead of an alkyne, a novel catalytic pathway was discovered leading to the formation of tetrahydroazepines, for which mechanistic rationale was provided. In this project we have successfully combined the goal of developing new synthetic methodologies with providing small molecule probes for biological research. The 139
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TRANSITION METAL-CATALYZED REACTION
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Transition Metal-Catalyzed Reaction
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List of Abbreviations Ac acetyl AcO
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Table of Contents 1.0 Introduction.
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Appendix A : X-ray crystal structur
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Table 4.8 Rh(I)-catalyzed cyclocarb
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List of Schemes Scheme 1.1 Three fo
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Scheme 3.24 Preparation of amide-te
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Scheme 4.16 Formation of bicyclo[5.
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1.0 Introduction 1.1 The Role of Di
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According to these guidelines, the
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Scheme 1.1 Three forms of diversity
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Another example from the Schreiber
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1.1.1 Transition Metal-Catalyzed Re
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37, , such reactions include transi
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the proximal olefin of allenyne 38
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2.0 Design and Synthesis of the Piv
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The allenic amino acid derivatives
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This protocol proved particularly u
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ZnCl2, which results in a Zn-chelat
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Scheme 2.7 Synthesis of trisubstitu
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THF), the yield was increased from
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the terminus of the alkyne led to d
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N-Alkylation of the glycine-derived
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circumvent this issue, variants suc
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BINAP as a chiral ligand to obtain
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stereochemistry of the exocyclic ol
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3.2 Rhodium(I)-Catalyzed Allenic Cy
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exocyclic olefin geometry is not re
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3.2.1 Preparation of Enol-ether Tri
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Scheme 3.15 Synthesis of cycloisome
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Scheme 3.17 Cycloisomerization of a
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Scheme 3.19 Tandem cycloadditions o
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Scheme 3.21 Intermolecular Diels-Al
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attractive, since additional functi
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increased yield of the triene (47%)
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as an isobutyl-amide 155b was prepa
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group) demonstrated that this cyclo
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in 1M HCl/dioxane (1 : 1) for 1h, t
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ppm (dd, J = 7.1, 4.6 Hz, 1H) assig
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http://ccc.chem.pitt.edu/). Using f
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Notably, exclusive cycloisomerizati
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intermediate in the reaction we sou
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epulsive dipole interactions (Schem
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Table 3.4 Diels-Alder reactions of
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allenic Alder-ene reaction, ene-all
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Figure 3.4 Examples of natural prod
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species onto the proximal double bo
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Scheme 3.49 Rh(I)-catalyzed ene rea
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y Magnus 144 and it involves the in
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usually is DMSO. Heating to 100 ºC
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that require high pressures of CO.
Page 105 and 106: In contrast to the Mo(CO)6-mediated
Page 107 and 108: Scheme 4.15 Rh(I)-catalyzed allenic
Page 109 and 110: 4.2 Rhodium(I)-Catalyzed Cyclocarbo
Page 111 and 112: lack of double bond selectivity, si
Page 113 and 114: Table 4.2 Cyclocarbonylation reacti
Page 115 and 116: Notably, the allenic cyclocarbonyla
Page 117 and 118: Scheme 4.22 Cyclocarbonylation reac
Page 119 and 120: neat or in solution. This decomposi
Page 121 and 122: the newly synthesized fulvenes (e.g
Page 123 and 124: stereocenters and mixture of E/Z is
Page 125 and 126: proximal double bond to give α-alk
Page 127 and 128: the methyl ester and Ha are syn. Sc
Page 129 and 130: that the major diastereomer in the
Page 131 and 132: We were motivated to first examine
Page 133 and 134: Scheme 4.42 Synthesis of pyrrole 29
Page 135 and 136: periodic acid (H5IO6). 209 These hi
Page 137 and 138: eaction failed to go to completion,
Page 139 and 140: 4.5.2 Synthesis of a Library of Tri
Page 141 and 142: diketones 312{1-3,1-2} in yields ra
Page 143 and 144: Figure 4.2 Distribution for physico
Page 145 and 146: tricyclic pyrrole 314{3,2,26} (Figu
Page 147 and 148: 4.6 Synthesis of α-Alkylidene Cycl
Page 149 and 150: anched and linear carboxylic acid i
Page 151 and 152: eactivity of the species prepared i
Page 153 and 154: considerably lower than the ratio o
Page 155: diastereomer. Next, allenyne 328 wa
Page 159 and 160: Experimental Section General Method
Page 161 and 162: General procedure A for esterificat
Page 163 and 164: F Bz N H 56f 2-Benzoylamino-3-(4-fl
Page 165 and 166: MeO2C Bz N H 58c 2-Benzoylamino-2-m
Page 167 and 168: MeO MeO2C Bz N H 58e 2-Benzoylamino
Page 169 and 170: mL) and MeOH (10 mL) instead of sat
Page 171 and 172: hexanes-EtOAc, 19 : 1 to 4 : 1, v/v
Page 173 and 174: which was immediately used in the C
Page 175 and 176: Boc TMS N H Bn 64f tert-Butyl-1-((4
Page 177 and 178: MeI (38 µL, 0.62 mmol). Yield 65a
Page 179 and 180: with brine and concentrated under v
Page 181 and 182: H MeO 2C • H Bn NHBoc tert-Butyl-
Page 183 and 184: TMS MeO 2C • 70 H H NHBoc 2-tert-
Page 185 and 186: 185 (10), 141 (21), 57 (100); EI-HR
Page 187 and 188: dispersion in mineral oil, 1.0 mmol
Page 189 and 190: EI-HRMS calcd for C30H26NO3 m/z [M-
Page 191 and 192: CbzN MeO 2C Me 73h 2-[Benzyloxycarb
Page 193 and 194: CbzN MeO 2C Me 2-(Benzyloxycarbonyl
Page 195 and 196: dispersion in mineral oil, 3.85 mmo
Page 197 and 198: completion of the addition, the rea
Page 199 and 200: BzN MeO 2C S 74h 2-(Benzoylprop-2-y
Page 201 and 202: BzN MeO 2C Bn 75b 2-(Allylbenzoylam
Page 203 and 204: BzN MeO 2C TBSO 75e 2-(Benzoylbut-2
Page 205 and 206: Hz, 1H), 5.85 (s, 1H), 5.52 (dd, J
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1H), 3.69 (s, 3H), 1.58 (d, J = 7.1
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µmol), [Rh(CO)2Cl]2 (1 mg, 3 µmol
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1.25 (m, 6H), 0.88 (t, J = 6.9 Hz,
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6.72 (d, J = 7.6 Hz, 0.5H), 6.68 (d
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BzN MeO2C Bn 122a Methyl-2-(N-(but-
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Bz N MeO2C Bn 1-Benzoyl-2-benzyl-4-
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13.9, 5.3 Hz, 1H), 2.51-2.47 (m, 1H
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15 min the solvent was removed unde
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Benzoyl chloride (0.169 mL, 1.46 mm
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mg, 0.11 mmol), [Rh(CO)2Cl]2 (4 mg,
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mL). kk The aqueous layer was extra
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ºC. After quenching the reaction b
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129.8, 129.0, 128.7, 128.4, 126.2,
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MeO 2C O O O N H N R 1 O N Ph [10c-
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The crude residue was purified by f
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14.4 Hz, 1H), 3.49-3.39 (m, 2H), 3.
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1H), 5.49 (dd, J = 17.3, 1.8 Hz, 1H
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was stirred at rt for 1 h when it w
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BzN HOOC 2-(N-(but-2-ynyl)benzamido
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°C and DIBAL-H (0.440 mL of a 1.0M
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129 (62), 91 (100); EI-HRMS calcula
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(d, J = 18.0 Hz, 1H), 4.14 (d, J =
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4.98 (dt, J = 7.7, 5.1 Hz, 1H), 4.1
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N Bz MeO2C OTBS 214 1-Benzoyl-2-(te
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270a (major diastereomer-eluting fi
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CDCl3): δ 7.42-7.17 (m, 13H), 7.04
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18.6 Hz, 1H), 4.34 (d, J = 18.0 Hz,
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Bz N MeO2C 2-Benzoyl-3,7-dimethyl-6
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v/v) afforded a mixture of compound
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(435 mg, 1.21 mmol), DMSO (429 µL,
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4.02 (s, 1H), 3.88 (s, 3H), 1.82 (s
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(207 mg, 96%) consisting of 287e (7
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procedure O, using: 74f (110 mg, 0.
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Bz N O H CO2Me BocN 287i 3-(2-Benzo
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4.17 (d, J = 15.0 Hz, 1H), 4.10 (d,
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137.1, 136.9, 130.4, 129.8, 128.5,
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H BzN MeO2C Bn H N C3H7 298b CO 2Me
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NMR (75 MHz, CDCl3): δ 172.3, 169.
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following the general procedure Q,
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H BzN MeO2C Bn H 5-Benzoyl-1,4-dibe
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119.9, 114.1, 109.9, 108.6, 73.0, 5
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4.11 (m, 1H), 4.07-3.98 (m, 1H), 3.
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126.8, 126.2, 109.0, 72.9, 58.7, 56
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NMR (75 MHz, CDCl3): δ 172.2, 169.
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3.0 Hz, 1H), 5.82-5.80 (m, 1H), 5.2
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87%). The diastereomeric ratio (288
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APPENDIX A: X-ray crystal structure
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APPENDIX B: X-ray crystal structure
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APPENDIX C: X-ray crystal structure
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APPENDIX D: X-ray crystal structure
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APPENDIX E: X-ray crystal structure
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APPENDIX F: QikProp property predic
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1 H and 13 C NMRs of 74b 293
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1 H and 13 C NMRs of 111a 295
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Page 317 and 318:
Page 319 and 320:
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1 H and 13 C NMRs of 270h 303
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1 H and 13 C NMRs of 307 307
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1 H and 13 C NMRs of 308n 309
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10. (a) Burke, M. D.; Schreiber, S.
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Hu, Y. J. Comb. Chem. 2006, 8, 286.
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49. For reviews on reactions of all
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69. (a) Trost, B. M.; Lautens, M.;
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containing cross-conjugated trienes
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Vaillancourt, J.; Rasper, D. M.; Ta
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130. Oppolzer, W.; Snieckus, V. Ang
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149. (a) Hicks, F. A.; Buchwald, S.
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Maiese, W. M. J. Antibiot. 2000, 53
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192. The mechanism of decomposition
Page 349 and 350:
Boger, D. L.; Boyce, C. W.; Labroli
Page 351:
Generated Inhibitors of Human Mitog
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