D A. Evans Polyene Cyclizations http://www.courses.fasharvardedu/-chem206/ Several Complex Mechanisms 206 Advanced Organic Chemistry OHC Handout 32 A 2. HOAC, NHO Introduction to Carbonium Ions-4 Angew. Chem. Int. Ed. Engl. 1978, 17, 476 J. Org. Chem.1990,57,2544 Stabilized Carbocations: Oxo-Carbenium lons(C=OR(+) Introduction to Terpene Biosynthesis Squalene, Lanosterol, Cholesterol Biosynthesis TFA, reflux Polyene Cyclization Chiral Acetals as C=O auxiliaries TIPS Bu3SnH Reading Assignment for this Lecture: Carey& Sundberg, Advanced Organic Chemistry, 4th Ed A. P. Johnson et al. Jcs Chem. Commun. 1994. 6. 765 Part A Chapter 5, Nucleophilic Substitution, 263-350 That outpost of empire Australia Heathcock, C H (1992). The enchanting alkaloids of Yuzuriha. " Angew.i produces some curious mammalia, the kangaroo rat, Other Excellent References the blood-sucking bat and Aurthur Birch, inter alia et, P. A (1984). "Olefin Cyclisation Processes That Form Carbon- etric Synthesis. Stereodifferentiating Reactions Part. J.D. Morrison New york. AP. vol 3: 341 If you are anxious for over-exposure, to prepublication disclosure, Thebtaranonth, C and Y. Thebtaranonth(1994). "Cyclization Reactions Boca Raton. FL. CRC Press Sir John Cornforth to good food and good drink, without leisure to think Corey Liu, enzyme"Mechanism for Polycyclic Triterpene Formation, Angew. Chem. Int Ed 2000, 39, 2812-2833 IUPAC symposia Matthew D Shair Monday December 9. 2002D. A. Evans Chem 206 Matthew D. Shair Monday, December 9 , 2002 http://www.courses.fas.harvard.edu/~chem206/ Reading Assignment for this Lecture: Polyene Cyclizations Carey & Sundberg, Advanced Organic Chemistry, 4th Ed. Part A Chapter 5, "Nucleophilic Substitution", 263-350 . Chemistry 206 Advanced Organic Chemistry Handout 32A Introduction to Carbonium Ions–4 ■ Stabilized Carbocations: Oxo–Carbenium Ions (C=OR(+)) ■ Introduction to Terpene Biosynthesis ■ Squalene, Lanosterol, & Cholesterol Biosynthesis ■ Polyene Cyclizations ■ Chiral Acetals as C=O Auxiliaries NMe O Br OMe O TIPSO N O O Me O TFA, reflux Bu3SnH A. P. Johnson et al., JCS Chem. Commun. 1994, 6, 765 OHC Me Me Me OBn OHC HN Me OBn Me 2. HOAc, NH Me 4OAc 75% Heathcock, C. H. (1992). “The enchanting alkaloids of Yuzuriha.” Angew. Chem., Int. Ed. Engl. 31: 665. (handout) Other Excellent References Thebtaranonth, C. and Y. Thebtaranonth (1994). "Cyclization Reactions". Boca Raton, FL, CRC Press. Bartlett, P. A. (1984). "Olefin Cyclisation Processes That Form Carbon￾Carbon Bonds". Asymmetric Synthesis. Stereodifferentiating Reactions, Part B. J. D. Morrison. New York, AP. vol 3: 341. Several Complex Mechanisms Angew. Chem. Int. Ed. Engl. 1978, 17, 476. J. Org. Chem. 1990, 57, 2544. 1. MeNH2 Corey & Liu, enzyme "Mechanism for Polycyclic Triterpene Formation," Angew. Chem. Int Ed. 2000, 39, 2812-2833 "That outpost of empire Australia, produces some curious mammalia, the kangaroo rat, the blood-sucking bat, and Aurthur J. Birch, inter alia." If you are anxious for over-exposure, to prepublication disclosure, to good food and good drink, without leisure to think, try IUPAC symposia." Sir John Cornforth: