Evans. Breit Electrocyclic Processes-3: 3-Atom Electrocyclization Chem 206 dis-out Solvolysis Summary Three-Atom Electrocyclization (4 electrons) Unfavorable favorable TsO Me D22 Con?? relative rate 1 Ring-fused Cyclopropyl Systems 0Q0 When the cis substiltutents on the cyclopropyl ring are tied together 00 in a ring the following observations have been made nonbond Tso favored nIon elative rate:>10 H2c 仓CH disavowed dis-out Observation COmE COm Con Revisiting the Favorski rearrangement: (Carey, Part A, pp 506-8) MeO2C / COmE MeO2C (+)…(H2C H2C CH2 TsO H H H H TsO H H O Cl H TsO O– Cl H TsO Me Me H H TsO H H H H TsO H H –Cl– O– H TsO H H Me Me O Y3 Y1 Y2 A H R H A R C B A B A Ar N CO2Me CO2Me H H Ar N CO2Me H H MeO2C R C A H H A MeO2C N MeO2C Ar C C R C B A B A N MeO2C Ar CO2Me A A R H H Electrocyclic Processes-3: 3-Atom Electrocyclizations Chem 206 Three-Atom Electrocyclizations (4 electrons) Dis?? Con?? Evans, Breit nonbonding cation anion Observation ·· ·· (–) (+) ·· (–) (+) Con Con Con ·· ·· relative rate 1 4 40,000 Solvolysis Summary Unfavorable favorable Ring-fused Cyclopropyl Systems When the cis substiltutents on the cyclopropyl ring are tied together in a ring the following observsations have been made dis-in dis-in dis-out dis-out favored disavored relative rate: > 10+6 Revisiting the Favorski rearrangement: (Carey, Part A, pp 506-8) base dis-in 3-exo-tet disallowed products