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rings5 - FIVE-MEMBERED RING FORMATION 5 Membered Rings HO...

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FIVE-MEMBERED RING FORMATION 138 5 Membered Rings PGF 2 α PGE 2 HO HO CO 2 H OH CO 2 H OH HO O Me Me Me Me H Me Me Me Me Hirsutene Isocumene Modhephane 1. Intramolecular S N 2 Reactions 2. Intramolecular Aldol Condensation and Michael Addition 3. Intramolecular Wittig Olefination 4. Ring Expansion and Contraction Reactions a. 3 5 b. 4 5 c. 6 5 5. 1,3-Dipolar additions 6. Nazarov Cyclization 7. Arene-Olefin Photocyclization 8. Radical Cyclizations 9. Others Synthesis 1973 , 397; ACIEE 1982 , 21 , 480; Intramolecular S N 2 Reaction 5-exo-tet: favored O Br LDA O JCSCC 1973 , 233 O Br CO 2 Me O CO 2 Me O CN O CN OH JACS 1974 , 96 , 5268
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FIVE-MEMBERED RING FORMATION 139 RO 2 C CO 2 R O O Cl Cl RO 2 C CO 2 R JACS 1979 , 101 , 5081 O TsO O NaH, DMSO JCSCC 1979 , 817 Intramolecular Aldol Condensation 5-exo-trig: favored intramolecular aldol condensation of 1,4-diketones O O R' R O R' R O O CH 3 CH 3 O CH 3 CH 3 TL 1982 , 29, 2237 O Br CO 2 Me O Br CO 2 Me O NaOMe, MeOH JACS 1980 , 102 , 4262 O O O NaOH O O JOC 1983 , 48 , 1217 Intramolecular Michael Addition 5-exo-tet: favored Organic Reactions 1995 , 47 , 315-552 O MeO 2 C O O O JACS 1979 , 101 , 7107
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FIVE-MEMBERED RING FORMATION 140 Intramolecular Wittig Olefination Tetrahedron 1980 , 36 , 1717 O C 5 H 11 THPO OTHP O 1) (MeO) 2 P(O)CH 2 - 2) Collins C 5 H 11 THPO OTHP O O P(OMe) 2 O base C 5 H 11 THPO OTHP O C 5 H 11 HO OH CO 2 H JOC 1981 , 46 , 1954 Ring Expansion Reactions - 3 5: Vinyl Cyclopropane Rearrangement Organic Reactions 1985 , 33, 247. O O O H O O H O SPh 2 _ O O H OTMS O O H TMSO JACS 1979 , 101 , 1328 - 4 5: Reaction of cyclobutanones with Diazomethane O Cl Me CH 2 N 2 O Me Cl Me Me O Cl Cl CH 2 N 2 Me O Cl Cl Me TL 1980 , 21 , 3059 O Cl Cl O CH 3 CH 3 Ph O CH 3 CH 3 Ph O Cl Cl CH 2 N 2 JACS 1987 , 109 , 4752
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FIVE-MEMBERED RING FORMATION 141 Ring Contraction Reactions - 6 5: Favorskii Reaction Organic Reactions 1960 , 11 , 261 Cl O O CO 2 H _ _ OH - O OH 1,3-Dipolar Addition to Olefins 1,3-Dipolar Cycloaddition Chemistry , vol 1 & 2 (A. Padwa ed.) (Wiley, NY 1984); ACIEE 1977 , 16 , 10. Chem Rev. 1998 , 98 , 863. a b c + _ 1,3-Dipole (4 π ) LUMO Alkene (2 π ) HOMO 4 π s + 2 π s - trimethylenemethane (TMM) ACIEE 1986 , 25 , 1. Synlett 1992 , 107.
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