Über die Entstehung von α‐Keto‐carbonium‐Ionen bei der säurekatalysierten Hydrolyse von Diazoketonen. (Vorläufige Mitteilung)

Abstract

Summary. Secondary deactivated aliphatic diazo compounds (diazo-ketones R-CO-CN,-R'; diazo-esters ROOC-CN,-R'; 1,1, I-trifluoro-2-diazopropane) are hydrolyscd by the A -S E~ mechanism comprising rate determining protonation of the substrate, followed by decomposition. Product analysis shows that the dccomposition of the secondary diazonium ions is monomolccular, without intervention of a nucleophile.The corresponding primary diazo compounds (R-CO-CHN,, ROOC-CHN, and CF,-CHN,) are hydrolysed by the A-2 mechanism comprising preequilibrium protonation; the primary diazonium ion reacts with a nucleophilc in a bimolecular displaccmcnt step .The only exception observcd is found in p-nitrophenyl-diazomethane, which follows A -S E~ mechanism.The observations are discussed in terms of the stability of the corrcsponding secondary resp. primary cc-keto-carbonium ions.Primare Diazoketone R-CO-CHN, werden bei der sauren Hydrolyse rasch und reversibel protoniert, worauf das gebildete Diazonium-Ion im geschwindigkeitsbestimmenden Schritt zu den Produkten zersetzt wird Wir fanden, dass auch anderweitig desaktivierte Diazoalkane wie 2,2,2-Trifluordiazoathan CF3-CHN, rasch und reversibel protoniert werden. Der Nachweis der Reversibilitat erfolgte wie in anderen Fallen [a]

2,2,2-Trifluorodiazoethane (CF3CHN2): A Long Journey since 1943

“…The reaction proceeded at room temperature and worked for aromatic (66), heteroaromatic (67), and aliphatic (68) substrates. Mechanistically, difluorocyclopropene 69 and CF 3 CHN 2 (1) first underwent [3 + 2]-cycloaddition into intermediate 70 (Scheme 14).…”

“…The hydrolysis was performed at room temperature (Scheme 38). 66 In 1979, Fields and Tomlinson observed that CF 3 CHN 2 (1) reacted with trifluoroacetonitrile to form N-alkylated product 127 in 84% yield (Scheme 26). 2 The first systemic study on the reaction of CF 3 CHN 2 (1) with nucleophiles was performed by Dorn and Koller in 1982 (Scheme 39).…”

“…This protecting group was also stable (a) under Scheme 38. Reaction of CF 3 CHN 2 (1) with Acids 13,65,66 Scheme 39. Reaction of CF 3 CHN 2 (1) (1) reacted with (CF 3 CO) 2 O without a base at room temperature to give the Cacylation product 204 in 82% yield (Scheme 42).…”

Echanges isotopiques d'hydrogène T‐H, T‐D, D‐H et H‐D de la diazoacétone et du diazoacétaldéhyde: Vitesse de protonation et effets isotopiques. Communication préliminaire

“…En effet, dCjk les homologues secondaires des diazoiques susmentionnCs prCsentent la protonation du carbone normale dCterminant la vitesse de la &action (mbcanisme A S & ) [4]. I1 serait donc trks intkressant de comparer les &apes de protonation du carbone en prCCquilibre ctrapide,, avec les protonations ctlentesa du type A -S E~.…”

The Nitrosation of Primary Aliphatic Diazocarbonyl Compounds: Formation of α‐carbonyl nitrile oxides. Preliminary communication

“…By analogy with reversible protonation, this can be expected for primary diazo compounds (-CHN,) deactivated by electron withdrawing groups like ROOC-, R-CO-[12j, I?&- [13] or ArS0,. In diazoalkanes, however, protonation is slower than loss of N,; in agreement with this, we never observed the formation of nitrile oxides, nor of products formed from them, starting with diazoethane, diazopropane, diazoisobutane, or plienyldiazometliane 6 ) .…”