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used this reaction to craft an approach towards to naturally occurring antibiotic guanacastepene A (267). 169, 170 To this end, reaction of allenyne 268 with 10 mol% [Rh(CO)2Cl]2 at 80 °C affords the [6,7,5]-fused tricyclic enone 269 in 65% yield (Scheme 4.17). Scheme 4.17 Allenic cyclocarbonylation reaction toward the synthesis of guanacastepene A. PO PO 10 mol % [Rh(CO) 2Cl] 2 R • CO (1 atm), toluene, 80 PO PO R O HO O O OAc oC 65% 268 269 267 - guanacastepene A P = TBS R = DPS In summary, the allenic cyclocarbonylation reaction has proven as a useful method for the synthesis of α- and 4-alkylidene cyclopentenones. The regioselectivity can be controlled by the choice of metal used to effect the reaction, thereby allowing for conversion of a single precursor to two structurally distinct products. 90
4.2 Rhodium(I)-Catalyzed Cyclocarbonylation of Amino-Ester Tethered Allenynes for Preparation of 4-Alkylidene Cyclopentenones Our next goal was to demonstrate that the amino ester-tethered allenynes could be used in the preparation of 4-alkylidene cyclopentenones via a selective cyclocarbonylation reaction with the distal double bond of the allene. In 2002, Brummond and coworkers reported that [Rh(CO)2Cl]2 effectively catalyzes the cyclocarbonylation reaction of variety of allenynes, selectively affording 4-alkylidene cyclopentenones. 165 In all reported cases, product formation was effected under 1 atm of CO and heating to 90 °C in toluene. In sharp contrast, when allenyne 73f was subjected to 5 mol% [Rh(CO)2Cl]2 in toluene under 1 atm of CO, reaction proceeded at rt to give only the cross-conjugated triene 111f in 77% yield and none of the expected cyclopentenone 270f (Scheme 4.18). Scheme 4.18 Attempted cyclocarbonylation reaction of 73f. CbzN MeO 2C • H 5 mol % [Rh(CO) 2Cl] 2 toluene, CO(1atm), rt, 1h Cbz MeO 2C 73f 270f (not observed) N O Cbz MeO 2C N 111f (77%) This result was somewhat anticipated since it was already established that cycloisomerization of the amino-ester tethered allenynes proceeds at an exceedingly fast rate (less than 10 min in presence of 5 mol % [Rh(CO)2Cl]2). Performing the reaction under CO atmosphere only noticeably slowed the rate of the cycloisomerization (1h vs. 10 min). It was rationalized that both triene 111f and cyclopentenone 270f are formed from a common Rh(III)-metallocyclopentene intermediate 271 as shown in Scheme 4.19. The 91
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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
Page 57 and 58: exocyclic olefin geometry is not re
Page 59 and 60: 3.2.1 Preparation of Enol-ether Tri
Page 61 and 62: Scheme 3.15 Synthesis of cycloisome
Page 63 and 64: Scheme 3.17 Cycloisomerization of a
Page 65 and 66: Scheme 3.19 Tandem cycloadditions o
Page 67 and 68: Scheme 3.21 Intermolecular Diels-Al
Page 69 and 70: attractive, since additional functi
Page 71 and 72: increased yield of the triene (47%)
Page 73 and 74: as an isobutyl-amide 155b was prepa
Page 75 and 76: group) demonstrated that this cyclo
Page 77 and 78: in 1M HCl/dioxane (1 : 1) for 1h, t
Page 79 and 80: ppm (dd, J = 7.1, 4.6 Hz, 1H) assig
Page 81 and 82: http://ccc.chem.pitt.edu/). Using f
Page 83 and 84: Notably, exclusive cycloisomerizati
Page 85 and 86: intermediate in the reaction we sou
Page 87 and 88: epulsive dipole interactions (Schem
Page 89 and 90: Table 3.4 Diels-Alder reactions of
Page 91 and 92: allenic Alder-ene reaction, ene-all
Page 93 and 94: Figure 3.4 Examples of natural prod
Page 95 and 96: species onto the proximal double bo
Page 97 and 98: Scheme 3.49 Rh(I)-catalyzed ene rea
Page 99 and 100: y Magnus 144 and it involves the in
Page 101 and 102: usually is DMSO. Heating to 100 ºC
Page 103 and 104: that require high pressures of CO.
Page 105 and 106: In contrast to the Mo(CO)6-mediated
Page 107: Scheme 4.15 Rh(I)-catalyzed allenic
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 and 156: diastereomer. Next, allenyne 328 wa
Page 157 and 158: Conclusions In summary, we have dem
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Experimental Section General Method
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General procedure A for esterificat
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F Bz N H 56f 2-Benzoylamino-3-(4-fl
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MeO2C Bz N H 58c 2-Benzoylamino-2-m
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MeO MeO2C Bz N H 58e 2-Benzoylamino
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mL) and MeOH (10 mL) instead of sat
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hexanes-EtOAc, 19 : 1 to 4 : 1, v/v
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which was immediately used in the C
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Boc TMS N H Bn 64f tert-Butyl-1-((4
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MeI (38 µL, 0.62 mmol). Yield 65a
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with brine and concentrated under v
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H MeO 2C • H Bn NHBoc tert-Butyl-
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TMS MeO 2C • 70 H H NHBoc 2-tert-
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185 (10), 141 (21), 57 (100); EI-HR
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dispersion in mineral oil, 1.0 mmol
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EI-HRMS calcd for C30H26NO3 m/z [M-
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CbzN MeO 2C Me 73h 2-[Benzyloxycarb
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CbzN MeO 2C Me 2-(Benzyloxycarbonyl
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dispersion in mineral oil, 3.85 mmo
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completion of the addition, the rea
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BzN MeO 2C S 74h 2-(Benzoylprop-2-y
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BzN MeO 2C Bn 75b 2-(Allylbenzoylam
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BzN MeO 2C TBSO 75e 2-(Benzoylbut-2
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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:
Page 321 and 322:
1 H and 13 C NMRs of 270h 303
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Page 325 and 326:
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
Page 335 and 336:
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
Page 343 and 344:
149. (a) Hicks, F. A.; Buchwald, S.
Page 345 and 346:
Maiese, W. M. J. Antibiot. 2000, 53
Page 347 and 348:
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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