T. V. RajanBabu
Dept of Chemistry, The Ohio State University
Chemistry 547 (Weeks 5 and 6)
Course Outline
Instructor: T. V. RajanBabu (rajanbabu.1@osu.edu), Room 353 Chemistry Annexe
Place and Time: Room 350 Chemistry Annexe, Wed, Fri 9:30-11:00
Office Hours: I plan to be in the department Mon-Sat 9:00 AM-6:00 PM. I can meet
with you right after class or make an appointment in person or via e-mail.
Quiz and Examination: You will be tested on the material covered in a quiz and the
mid-semester examination. I urge you to read the handouts which should help you
prepare for the tests.
They have been posted on my website
https://web.chemistry.ohio-state.edu/~rajanbabu/courses.php. I will also provide some
sample questions.
Periodically check this website for further information and
announcements about the course.
Lecture 1. Fundamentals of Catalysis. Definition, reaction coordinate diagram,
how does it work?, homogeneous catalysis, example of Rh(I)-catalyzed hydrogenation,
mechanism, what is a catalytic cycle?, fundamental organometallic processes (ligand
substitution, oxidative addition, migratory insertion, transmetallation, reductive
elimination, illustrate with Rh(I)-catalyzed hydrogenation, Why transition metals are
effective as homogeneous catalysts?, turnover limiting step, features of a catalytic
process, “Effective Atomic Number Rule (18-electron-rule)” and how is related to
catalysis, formal oxidation states, d-electron-configuration and coordinately saturated
and unsaturated complexes, ligand classes, counting electrons with examples, examples
of reactivity and example of diverse reactivity allyl Pd and allyl Ni systems, catalyst
types and examples: Lewis acid-catalyzed reactions (no change in metal oxidation state,
Pd-catalyzed allylation, a typical Pd-catalyzed cross-coupling reaction (Mn/Mn+2 systems)
Lecture 2. Stereochemistry and Selectivity: Concepts and Definitions (What
you need to know to read and understand a topical publication). Why worry
about selectivity- major challenges in organic synthesis- ‘molecules in the news
(handout)’, uncommon reactions of readily available materials to make useful products,
highly selective methods for ‘green’ manufacturing. Examples. ‘Selectivity’ is the key
word! Fundamental concepts and definitions: chemoselectivity, regioselectivity,
stereoselectivity (diastereoselectivity and enantioselectivity), Glossary of Problematic
Terms in Organic Stereochemistry (handout).
Isomers: constitution, configuration (stereoisomers) enantiomers and
diastereomers, examples, conformation (chair-boat, also helical or atropisomerism),
stereochemical terms-a primer (handout), optical activity, methods for determination of
enantiomeric excess-chiral stationary phase (CSP) GC and CSP-hplc, nmr
T. V. RajanBabu
Dept of Chemistry, The Ohio State University
Sources of chirality: asymmetric chiral center (C or heteroatom), chirality in tertamines vs tert-phosphines, specifying chirality priority rules and CIP notation, specifying
helical chirality (e. g., Biaryls, handout: chirality without chiral center), allenes
Diastereomers and diastereomeric relationships, difference in properties,
specifying diastereomers: E, Z nomenclature, threo/erythro nomenclature, syn and anti
nomenclature; example aldol reaction of methyl propionate and acetaldehydespecifying product configurations.
Lecture 3. Stereochemistry and Selectivity. Concepts and Definitions
(continued)
Consequences of diastereoisomerism: (i) resolution of enantiomers
via formation of diastereomeric salts, (ii) resolution via chromatography (GC and HPLC),
(iii) identification of absolute stereochemistry, (iv) determination of enantiomeric ratio
(er), or enantiomeric excess (ee), NMR shift reagents, (iv) diastereoselective synthesis,
(v) kinetic resolution, examples and (vi) enantioselective synthesis, examples.
• Selectivity vs Specificity an important distinction (handout).
•
Hammond Postulate, Kinetic and Thermodynamic Control.
Kinetic and
thermodynamic control, use of energy diagrams, examples: DBr addition to 1,3butadiene, enolate formation from 2-methylcyclohexanone, Hammond postulate
(Definition IMPORTANT!) examples: Markovnikov regioselectivity of HX addition to
monosubstituted alkenes, Orientation in electrophilic aromatic substitution reactions
Lecture 4. Asymmetric Catalysis Using Organometallic Reagents. Hammond
Postulate and Curtin Hammett Concepts, Methods and Origin of Selectivity. CurtinHammett principle (Definition, IMPORTANT!) examples: reactivity of conformations
pyrolytic elimination, Felkin-Anh model for predicting acyclic stereoselection, [Rh(L*)]+
X– , L* =chiral ligand)]-catalyzed asymmetric hydrogenation of dehydroamino-acids for
the synthesis of enantiopure alpha-amino-acids Diastereomeric intermediates and origin
of selectivity, Pd(0)-catalyzed allylation of stabilized carbon nucleophiles and RhCatalyzed hydrogenation two classical examples with different reaction profiles.