Organic Mechanisms. Xiaoping Sun

with elemental bromine in water (a) and...FIGURE 3.34 Regiochemistry and stereochemistry for reactions of 1‐methylcycl...

      4 Chapter 4FIGURE 4.1 Prototype for electrophilic cycloaddition of an alkene forming a ...FIGURE 4.2 Epoxidation of an alkene by a percarboxylic acid following a conc...FIGURE 4.3 Examples of alkene epxidation reactions.FIGURE 4.4 Mechanism for cycloaddition of dichlorocarbene (CCl₂) to an alken...FIGURE 4.5 Stereochemistry for cycloaddition of dichlorocarbene (CCl₂) to al...FIGURE 4.6 Removal of chloro groups (defunctionalization) from 1,1‐dicloropr...FIGURE 4.7 Stepwise radical mechanism for cycloaddition of the triplet diphe...FIGURE 4.8 Mechanism and stereochemistry for cycloadditions of a carbenoid t...FIGURE 4.9 π molecular orbital diagram of ethylene.FIGURE 4.10 Possible frontier molecular orbital (FMO) interactions between t...FIGURE 4.11 HOMO–LUMO electronic transition in ethylene.FIGURE 4.12 Possible frontier molecular orbital (FMO) interactions between a...FIGURE 4.13 Mechanism and stereochemistry for photochemical cycloaddition of...FIGURE 4.14 Mechanism and stereochemistry for photochemical cycloaddition of...FIGURE 4.15 Frontier molecular orbital (FMO) interactions involved in therma...FIGURE 4.16 Effect of an electron‐withdrawing group on the energy level of L...FIGURE 4.17 Examples of Diels–Alder reactions of 1,3‐butadiene derivatives w...FIGURE 4.18 Regiochemistry for Diels–Alder reaction.FIGURE 4.19 Diels–Alder reaction of 1,3‐cyclopentdiene with ethylene giving ...FIGURE 4.20 Diels–Alder reactions of the C=N containing t‐butyl 2‐azidoacryl...FIGURE 4.21 Diels–Alder reactions of 1,3‐cyclopentadiene with 2,3‐dicyano‐p‐...FIGURE 4.22 Diels–Alder reactions for larger cyclic systems.FIGURE 4.23 Regioselectivity and stereoselectivity for Diels–Alder reactions...FIGURE 4.24 Synthesis of tofogliflozin by a 6π intramolecular diene‐yne Diel...FIGURE 4.25 Frontier molecular orbital (FMO) interactions involved in therma...FIGURE 4.26 Overall mechanism for oxidation of an alkene to two carbonyl gro...FIGURE 4.27 Cycloaddition reaction of an alkene to diazomethane.FIGURE 4.28 (a) The in‐plane sideway overlaps of p orbitals in two perpendic...FIGURE 4.29 Thermally symmetry‐allowed cycloadditions of the dithionitronium...FIGURE 4.30 Mechanism for cycloaddition of an alkene to an alkene‐NS₂⁺ cyclo...FIGURE 4.31 Stereochemistry of cycloadditions of alkenes to alkene‐NS₂⁺ cycl...FIGURE 4.32 Cycloaddition of [S=N=S]⁺ to 2,3‐dimethyl‐2‐butene.FIGURE 4.33 Thermally symmetry‐allowed cycloadditions of [S=N=S]⁺ to alkynes...FIGURE 4.34 Mechanism for intramolecular ring‐closure (cyclization) of 1,3,5...FIGURE 4.35 Mechanism for the Cope rearrangement of deuterium isotope‐labele...FIGURE 4.36 Photochemical ring‐closure of 1,3‐butadiene to cyclobutene.FIGURE 4.37 The 4π‐cycloaddition between the N=N bonds. (a) Pathway for a re...FIGURE 4.38 The 4π‐cycloaddition of C₆₀ with 2,5‐dimethyl‐2,4‐hexadiene.FIGURE 4.39 The energetics of FMOs for the 4 π 1,3‐cyclopentadiene and 2 π e...FIGURE 4.40 Comparison of the 6 π Diels–Alder cycloadditions of a 1,3‐dipole...FIGURE 4.41 The energetics of FMOs for a 4 π 1,3‐dipole and the 2 π styrene ...FIGURE 4.42 The FMO interactions for the cycloaddition reaction of quadricyc...FIGURE 4.43 Chemical synthesis of Vitamin D₂ via the ring‐opening process of...FIGURE 4.44 The ribosome‐catalyzed formation of the peptide bond (C–N) in bi...

      5 Chapter 5FIGURE 5.1 General mechanism for the electrophilic aromatic substitution (EA...FIGURE 5.2 Formation of a stable arenium (σ‐complex) between hexamethylbenze...FIGURE 5.3 The full mechanism for the charge‐transfer aromatic nitration.FIGURE 5.4 Mechanism for the electrophilic substitution reaction of benzene ...FIGURE 5.5 Formation of a stable arenium (σ‐complex) between hexamethylbenze...FIGURE 5.6 Possible mechanism for the AlCl₃‐catalyzed electrophilic substitu...FIGURE 5.7 Possible mechanism for the AlCl₃‐catalyzed electrophilic aromatic...FIGURE 5.8 AlCl₃‐catalyzed electrophilic aromatic substitution of p‐toluenes...FIGURE 5.9 (a) Reaction of antimony pentachloride (SbCl₅) with hexamethylben...FIGURE 5.10 Unexpected ring‐opening process in the AlCl₃‐catalyzed Friedel–C...FIGURE 5.11 FeCl₃‐catalyzed EAS reactions of arenes with aldehydes.FIGURE 5.12 FeCl₃‐catalyzed intramolecular EAS reactions of benzyl alcohol d...FIGURE 5.13 FeCl₃‐catalyzed regioselective EAS reactions of alkenes and poss...FIGURE 5.14 Mechanism for the FeCl₃‐catalyzed reaction of chlorobenzene with...FIGURE 5.15 The d_π–pπ* back bonding between Fe(III) and the S=O bond in...FIGURE 5.16 Mechanism for AlCl₃‐catalyzed Friedel–Crafts reaction of benzene...FIGURE 5.17 Mechanism for AlCl₃‐catalyzed Friedel–Crafts reaction of benzene...FIGURE 5.18 Mechanism for AlCl₃‐catalyzed Friedel–Crafts reaction of benzene...FIGURE 5.19 Mechanism for acid‐catalyzed electrophilic substitution reaction...FIGURE 5.20 Mechanism for acid‐catalyzed electrophilic substitution reaction...FIGURE 5.21 Mechanism for an intramolecular electrophilic aromatic substitut...FIGURE 5.22 Mechanism for an electrophilic aromatic substitution reaction of...FIGURE 5.23 Mechanism for an intramolecular electrophilic aromatic substitut...FIGURE 5.24 Simplified and more subtle models for the charge distribution in...FIGURE 5.25 Common electron‐donating and electron‐withdrawing groups (EDG's ...FIGURE 5.26 The intermediate ortho‐, meta‐, and para‐arenium ions which bear...FIGURE 5.27 Chlorination of alkylbenzenes: Directing effects of different al...FIGURE 5.28 Reaction of phenol with bromine: Para‐directing effect of the hy...FIGURE 5.29 The intermediate ortho‐, meta‐, and para‐arenium ions which bear...FIGURE 5.30 Mechanism for proton‐catalyzed isomerization of 1,2,4‐tri(t‐buty...FIGURE 5.31 Mechanism for proton‐catalyzed dealkylation of 2,4‐dichlorocumen...FIGURE 5.32 Mechanism for acid‐catalyzed isomerization of α‐naphthalenesulfo...FIGURE 5.33 Metals (magnesium and lithium) facilitated electrophilic aromati...FIGURE 5.34 Metal directing groups (MDG's) facilitated lithiumation of arene...FIGURE 5.35 Reactions of substituted arenes with ^sBuLi followed by substitut...FIGURE 5.36 ortho‐Metal directing group facilitated lithiumation and subsequ...FIGURE 5.37 Nucleophilic aromatic substitution (NAS) of a halobenzene via th...FIGURE 5.38 Mechanism for nucleophilic substitution of the carbon‐14 isotope...FIGURE 5.39 Nucleophilic substitution reaction of o‐chlorotoluene with hydro...FIGURE 5.40 Nucleophilic substitution reactions of halobenzenes with cyanide...FIGURE 5.41 Nucleophilic substitution reactions of aryldiazonium (Ar–⁺N=N) f...FIGURE 5.42 Reaction of 2‐bromobenzoic acid with benzyl nitrile (C₆H₅CH₂CN) ...FIGURE 5.43 Nucleophilic aromatic substitution via the Meisenheimer complex....FIGURE 5.44 Reaction of 2,4‐dinitrochlorobenzene with hydrazine giving 2,4‐d...FIGURE 5.45 Nucleophilic substitution of 2,4‐difluoronitrobenzene with liqui...FIGURE 5.46 The azocoupling reaction between 1,3‐dinitrobenzene and aryldiaz...FIGURE 5.47 Structures of Combretastatin A‐4 (CA4) and modified analogues.FIGURE 5.48 Synthesis of the diaryl sulfide analogue of CA4 by nucleophilic ...FIGURE 5.49 The aryl‐sulfoxide‐containing nitrogen mustard and its in vivo r...FIGURE 5.50 Synthesis of a biomedically active aryl‐sulfoxide‐containing pol...FIGURE 5.51 Chemical synthesis of the inflammatory ibuprofen and the reactio...

      6 Chapter 6FIGURE 6.1 Super and very good leaving groups.FIGURE 6.2 Possible resonance structures for phenoxide and acetate, accounti...FIGURE 6.3 Reaction of sodium azide and (2S)‐2‐triflyloxyester in CH₃CN (an ...FIGURE 6.4 Reaction of trans‐1‐bromo‐4‐methylcyclohexane and sodium hydrogen...FIGURE 6.5 Effect of steric hindrance on relative rate constants for the S_N2...FIGURE 6.6 Effect of steric hindrance on relative rate constants for the S_N2...FIGURE 6.7 Destabilization of the S_N2 transition states by steric interactio...FIGURE 6.8 The S_N2 reactions of hydroxide and water with bromomethane: compa...FIGURE 6.9 Energy profiles for the S_N2 reactions in (1) a more polar protic ...FIGURE 6.10 Stabilization of the S_N2 transition state by an unsaturated grou...FIGURE 6.11 (a) Molecular orbitals (MOs) in CH₃X (X = Cl, Br, or I) which ar...FIGURE 6.12 (a) Maximum overlap of a nucleophile orbital with the 2p_z‐based ...FIGURE 6.13 (a) Molecular orbitals (MOs) in RCH₂X (X = Cl, Br, or I; R = alk...FIGURE 6.14 Occupied bonding molecular orbitals (MOs) in CH₂Cl₂ which are fo...FIGURE 6.15 Reaction profile for the S_N1 mechanism.FIGURE 6.16 The S_N1 reactions of 2‐chloro‐2‐methylpropane in protic solvents...FIGURE 6.17 The S_N1 rate constants for hydrolysis of various bromoalkanes....FIGURE 6.18 Energy profiles for rate‐determining steps of the S_N1