Dicyanmethylide, V. Darstellung und Reaktionen von Ammoniumdicyanmethyliden

Abstract

Die N-Dicyanmethylide 2b, 2d und 2f konnen aus den aromatischen Aminen l b , Id, I f und Diazomethandicarbonitril dargestellt werden. Die folgenden Reaktionen der Ylide 2 a -f werden mit denen der N-Oxide verglichen: thermische Zersetzung, Salzbildung und Umsetzung mit Triphenylphosphin. Dicyanomethylides, V1). -Preparation and Reactions of Ammonium DicyanomethylidesThe N-dicyanomethylides 2b, 2d and 2f can be prepared by the reaction of aromatic amines 1 b, 1 d, 1 f with diazomethanedicarbonitrile. The following reactions of the ylides 2 a -f are compared with those of N-oxides: thermal decomposition, salt formation and reaction with triphenylphosphine.

Cascade Processes of Metallo Carbenoids

“…Since their introduction in 1960, pyridine ylides have become increasingly popular probes of the dynamics of carbenes which lack chromophores. − The combination of high reactivity, favorable spectroscopic properties, and long ylide lifetime has allowed the study of the dynamics of a variety of “invisible” carbenes . The technique has found use in the study of aryl, arylhalo, alkyl, alkylalkoxy, alkylhalo, arylsiloxy, and dialkyl carbenes. − A number of examples dealing with the preparation of stable pyridinium ylides have also been reported in the literature. − Pyridinium tetraphenylcyclopentadienylide ( 277 ) was synthesized by irradiating 2,3,4,5-tetraphenyldiazocyclopentadiene ( 276 ) in pyridine. Addition of water precipitated the purple ylide 277 in almost quantitative yield 166-168 (Scheme ).…”

Ylide formation from the reaction of carbenes and carbenoids with heteroatom lone pairs

“…The potential for ylide formation by reaction of a nucleophilic heteroatom with an electron-deficient carbene has been exploited by Potts to prepare the mesoionic anhydro-4-hydroxythiazolium hydroxide system.135 A mixture of 3H-quinazoline-4-thione (275) and a-(tosylhydrazono)phenylacetyl chloride (276) in the presence of triethylamine gave diazothioamide 277. This compound afforded the aromatic mesoionic system tems was formed. This intramolecular carbenoid-type cyclization provides an efficient synthesis of the mesoionic thiazolium hydroxide dipole.…”

“…A number of examples dealing with the preparation of stable pyridinium ylides have been reported in the literature. [272][273][274][275][276] As early as 1960, pyridinium tetraphenylcyclopentadienylide (634) was synthesized by heating 2,3,4,5-tetraphenyldiazocyclopentadiene (633) at reflux in pyridine. Addition of water precipitated the purple ylide 634 in almost quantitative yield.272-274 This process appears to be general for a number of substituted pyridines (i.e.…”

Cyclative MCRs of Azines and Azinium Salts

“…Some of them are rendering reasonable stability and can even be isolated. [115] The catalytically generated in situ pyridinium ylides can also be reacted with electrophilic alkenes, however this aprotic route to pyridinium ylides has received little attention in MCRs to date. Padwa [116] and co-workers reported that in the presence of a catalytic amount of rhodium (II) octanoate, 2-(methylthio)pyridine (146) It did not take long, while the feasibility of the reaction has been demonstrated on a wide range of substrates.…”