This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: C C BOND FORMATION 115 C C Bond Formation 1. From other acetylenes 2. From carbonyls 3. From olefins 4. From Strained Rings 5. Eschenmosher Fragmentation 6. Allenes From Other Acetylenes- The proton of terminal acetylenes is acidic (pK a = 25), thus they can be deprotonated to give acetylide anions which can undergo substitution reactions with alkyl halides, carbonyls, epoxides, etc. to give other acetylenes. R H R R R 1 R OH R 2 R 3 R OH O R 2 R 3 O _ M + R 1-X Et 2 AlCl- Since the acetylenic proton is acidic, it often needs to be protected as a trialkylsilyl derivative. It is conveniently deprotected with fluoride ion. R H R SiR 3 R H F- B:, R 3 SiCl Acetylide anions and organoboranes R 1 _ Li + R 3 B R 1 BR 3 _ Li + I 2 R 1 R JOC 1974 , 39 , 731 JACS , 1973 , 95 , 3080 Palladium Coupling Reactions: iPr 3 Si SnBu 3 O O O O SiiPr 3 iPr 3 Si (Ph 3 P) 4 Pd JACS 1990 , 112 , 1607 Cl Cl C C BOND FORMATION 116 Br C 5 H 11 OTBS CO 2 Me OTBS OTBS Pd(Ph 3 P) 4 , CuI iPr 2 NH, PhH CO...
View Full Document