D. A. Evans Other Functional Groups with Non-alternate Reactivity Patterns Chem 206 The Diazo Functional Group Acid Catalyzed Reactions of Diazo Compounds H Review: Smith Tet. 1981 2407 a Both(+)and(-)reactivity patterns suggested by resonance structures H ■ Rxns with acids R时一NxH HCXN三N Diazocarbonyl Diazonium Common acids include BF3OEt2, HBF4. TFA, etc. N2=C-R N2=c-R Mechanism of activation is unclear for both Lewis and protic acids activation ay occur by protonation on C or o I Initiating reactivity is (-) subsequent reactivity is (+ a Ring expansion reactions: o Acid-Catalyzed Reactions EtoH N2-C-R N2-C-R N2-=C-R +) 96%) Mander. Chem. Comm. 1971773 N2-C-R Tet,1991134 Restriction: Starting ketone must be more reactive than product ketone become familiar with the peculiarities of a Precursors to Carbenes: N2C methane), it occurred to us that we might C=NEN N三N O filled( 25°C,2min Gibberellic Acid E EG H (82%) cs1980662H X C N N R H C N H R N C N N R H N2 C R N2 C R D N2 C O C N N R H H C N H R N – N N C H R E G C: H R C: H R EtOH CH2N2 HO CH2–N2 N2 C R C R H C N N R H O H C X H R N2 C R N N OMe O N2 Cl3COCO HO O N2 H3C CH3 O N N TFA H + O O OCOCCl3 O O H3C CH3 O N N N2 C R N2 C R N2 C R D. A. Evans Other Functional Groups with Non-alternate Reactivity Patterns Chem 206 ■ Initiating reactivity is (–); subsequent reactivity is (+) (+) (–) X + – – + ■ Rxns with acids: ■ Both (+) and (–) reactivity patterns suggested by resonance structures + – + – + – The Diazo Functional Group empty (+) filled (–) + – ■ Precursors to Carbenes: Restriction: Starting ketone must be more reactive than product ketone (+) (–) + ■ Ring expansion reactions: (–) (+) (+, –) –E,G Acid Catalyzed Reactions of Diazo Compounds Review: Smith, Tet. 1981 2407 Diazocarbonyl Diazonium Common acids include BF3 •OEt2 , HBF4 , TFA, etc. Mechanism of activation is unclear for both Lewis and protic acids; activation may occur by protonation on C or O Acid-Catalyzed Reactions -25°C, 2 min (82%) Gibberrellic Acid Mander, JACS 1980 6626 TFA, -20°C (96%) "Having become familiar with the peculiarities of diazoketone chemistry while preparing [other compounds] (and, I might add, inured to handling uncomfortably large quantites of diazomethane), it occurred to us that we might be able to substitute a diazo group for bromine." Lewis Mander Mander, Chem. Comm. 1971 773 Tet., 1991 134 (–) (–) (+)