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Advanced Organic Chemistry focusing on addition reactions

Advanced Organic Chemistry focusing on addition reactions. Electrophilic addition to C=C bonds. syn. anti. Stepwise mechanisms with intermediates as:. Type 1. Type 2. Type 3. Type 1. Type 2. carbenium ion stability: hyperconjugation. Wagner-Meerwein shift. anti. syn. Type 1.

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Advanced Organic Chemistry focusing on addition reactions

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  1. Advanced Organic Chemistry focusing on addition reactions Electrophilic addition to C=C bonds syn anti Stepwise mechanisms with intermediates as: Type 1 Type 2 Type 3

  2. Type 1 Type 2 carbenium ion stability: hyperconjugation Wagner-Meerwein shift

  3. anti syn Type 1 Type 2

  4. Syn addition Q1 tight ion-pair:very stable because of benzylic-type Cf. solvent-separated ion-pair

  5. Mechanistic Rationale

  6. Peroxide Effects no air, 25 ℃, 240 h Markovnikov rule air, 25 ℃, < 16 h R-O-O-R 2 R-O･ R-O･+ HBr R-OH+ Br･ + Br･ + HBr + Br･ O2 R-H R･　+ H-O=O･ Q2 R･　+ O2 R-O=O･ R-O=O･ + R･　 R-O=O-R R-O-O-R

  7. Addition of Br2 to C=C Double Bonds electrophilic, anti, stereospecific Br3－as nucleophile Bromonium ion Type-3 Type-1 anti

  8. Physical Evidence for Bromine-Olefin p-complex and Bromonium Ion

  9. Reaction Pathway Switching: low Br2 concentration, Wohl-Ziegler bromination NBS Free radical initiator radical chain

  10. Trapping of Bromonium Ions with Nucleophiles other than Br－ regioselective ring-opening Bromine syn-addition Q3

  11. Electrophilic Addition to Alkynes Type-A Type-B Type-C Linear: unstable Markovnikov rule

  12. Addition of Br2 to Carbon-Carbon Triple Bonds: Synthesis of trans-1,2-dibromo Olefins Vinylic SN1 Reaction: cation-stabilizing groups or good leaving groups

  13. Electrophilic Addition of Peracids or Hydroperoxides to C=C Bonds concerted Bartlett: 1957 Q4 Nucleophilic or 1,3-dipolar mechanism ? Relative rates with peracid at 25.7 ℃

  14. Epoxidation of Allylic Alcohols with Hydroperoxide Regeneration of catalyst t-BuOH + trigonal bypiramidal product trans-ligand effect ROH

  15. Hydroxy-directed and Diastereoselective Epoxidation

  16. Allylic Conformation and Strain most stable Allylic Strain: A1,3 3 2 1 Allylic Conformation

  17. Stereochemical Outcomes of two Representative Epoxidations transition-metal mediated t-BuOOH epoxidation hydroxy-directed peracid epoxidation

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