1.3‐Dipolare Cycloadditionen, XXXII. Kinetik der Additionen organischer Azide an CC‐Mehrfachbindungen

Abstract

rnDie zahlenmarJige Errnittlung der Dipolarophilen-Aktivitaten gestattet es, das AusmarJ der mechanistischen Gerneinsamkeit der Cycloadditionen verschiedener 1.3-Dipole zu beurteilen. Die Aktivitatsreihe gegeniiber Diphenylnitrilimin3), einem Glied der Reihe der Nitriliumbetaiue, sei hier rnit derjenigen des Phenylazids verglichen, das den Diazoniumbetainen4) angehort. Nach AbschluR unserer Versuche (1963) lag noch keine kinetische Studie der Azid-Addition vor. Inzwischen berichteten Scheiner und Mitarbb.5) iiber die Kinetik der Arylazid-Addition an Norbornen. Bailey und Whites) verglichen Pikryl-und Phenylazid i n der Reaktivitat gegenuber cyclischen und offenkettigen Alkenen. A. MethodeDie kinetische Verfolgung der kid-Addition griindet man zweckmaisig auf die sinkende Konzentration des organischen Azids. Die Reduktion des unverbrauchten Azids mit alkalischem Arsenit 7) und volumetrischer Messung des entbundenen Stickstoffs bewahrte sich nicht, da die Addukte a.P-ungesattigter Carbonylverbindungen unter diesen Bedingungen ebenfalls Stickstoff verlieren.

Highly accelerated inverse electron-demand cycloaddition of electron-deficient azides with aliphatic cyclooctynes

“…It must be noted, however, that the absolute rate constants as measured by this protocol are about twofold lower than those reported earlier in other solvent systems 1 . One sensible explanation lies in the fact that 1,3-dipolar cycloadditions generally proceed faster in a more polar environment (for example, 50% aqueous CH 3 CN) 23 , as for example was also demonstrated by us for strain-promoted nitrone cycloadditions 24 19,20 , reaction with BCN unexpectedly proceeded 2.9 Â faster in comparison with benzyl azide (A, entry 1). Thus, in a side-by-side comparison, reaction of phenyl azide with BCN is in fact 6 Â faster than with DIBAC, quite opposite to aliphatic azides.…”

Ruthenium-Catalyzed Azide Alkyne Cycloaddition Reaction: Scope, Mechanism, and Applications

“…44 As mentioned, different isomers can be obtained in the cycloaddition of alkyl and aryl azides with alkynes. While the original Huisgen reaction afforded mixtures of 1,4-and 1,5-disubstituted 1,2,3-triazoles, 32 and CuAAC selectively produced the 1,4-isomer, [4][5] there was a lack of robust methods for the exclusive formation of 1,5-disubstituted triazoles. Such compounds can be of interest in their own right, as the positioning of the two substituents on adjacent atoms can be advantageous in cyclization reactions, and the rigid cyclic structures of these products exploited in materials science applications.…”

“…[28][29][30] The first report of such a transformation dates back even further, to 1893, when Michael described the reaction of phenyl azide with dimethyl acetylenedicarboxylate. 31 However, many cycloadditions involving azides are impractically slow at ambient temperature, 32 and mixtures of 1,4-and 1,5-disubstituted triazoles are formed in the reaction with alkynes (Scheme 1). 28…”

Efficient synthesis of functionalized 1,2,3-triazoles by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide

“…6 In addition, these moieties are widely applied as photosensitizers, dyes, 7 and commercially employed as anti-corrosive agents 8 in industry. Owing to the importance of these compounds, a variety of methods are known in the literature for the synthesis of pyrazoles, which include the thermal 1,3-dipolar cycloaddition of azide with various alkynes 9 and cycloaddition reactions of terminal alkynes with alkyl azides using Cu(I) as catalyst. 10 In addition, these molecules can also be prepared in one-pot procedure from alkynes with azides.…”