Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• cyclic (alkyl)(amino) or mesoionic carbenes (CAACs or MICs) onto carbon disulfide. Nine novel compounds were isolated and fully characterized by 1H and 13C NMR, FTIR, and HRMS techniques. Moreover, the molecular structures of two CAAC·CS2 and two MIC·CS2 betaines were determined by X-ray diffraction

• analysis. The analytical data recorded for all these adducts were compared with those reported previously for related NHC·CS2 betaines derived from imidazolinium or (benz)imidazolium salts. Due to the absence of electronic communication between the CS2 unit and the orthogonal heterocycle, all the CAAC·CS2

• , MIC·CS2, and NHC·CS2 zwitterions displayed similar electronic properties and featured the same bite angle. Yet, their steric properties are liable to ample modifications by varying the exact nature of their cationic heterocycle and its substituents. Keywords: betaines; carbenes; ligand effects; nitrogen

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• compounds CH2XY in a 1:1:1 molar ratio to furnish 1-phosphonium-5-oxabetaines, Ph3P+–C(R)=CH–C(O–)=CXY. These betaines are formed preferentially, but not exclusively, as E-diastereoisomers with respect to the vinylic double bond. In some cases, separation of the two diastereoisomers was achieved by

• fractionating crystallization. Structure determination by X-ray diffraction analysis revealed marked conformational differences around the CH–C(O–) single bond of E and Z-isomers and extended charge delocalization in the anionic part. Keywords: betaines; multi-component reactions; N-triflylamides; phospha

• -Michael reaction; propiolamides; Introduction Beside the well-known phosphonium ylides (Wittig ylides, methylenephosphoranes), various other types of zwitterions containing a tetravalent phosphonium moiety (phosphonium betaines) exist. They are often considered as reaction intermediates, but reports on

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• and 5 have been optimized to give either 6 or 7 selectively, the undesired product could be detected in some cases by characteristic signals in the 1H NMR spectra of the crude product mixtures. It is reasonable to assume that the formation of betaines 7 according to method A (Scheme 3) proceeds via

• the neutral guanidine derivatives 6 as intermediates. In fact, the latter compounds are converted into betaines 7 under the same reaction conditions (method B). In terms of yields, however, the direct, one-step route (method A) turned out to be the better choice, as was found for betaines 7b–d (Table

• ) is generally considered as being typical for these and related mesoionic compounds (see the next chapter). It was therefore expected that betaines 7 would be attacked by electrophiles at the exocyclic nitrogen atom bearing excess π-electron density. In fact the protonation of 7b,c with hydrochloric

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• biological activities of NHC complexes [23][24]. In the last decade, attention has also been directed to anionic N-heterocyclic carbenes [25]. In this context, mesomeric betaines are interesting from two viewpoints. They are not only able to undergo tautomerisations to neutral NHCs and thus provide a safe

• been prepared from mesoionic compounds (Figure 1). The carbenes 3 [31] and 4 [32][33] originate from a conjugated ylide and a cross-conjugated mesomeric betaine, respectively. A review elucidates the interconversions of mesomeric betaines to different types of N-heterocyclic carbenes (NHC, aNHC, rNHC

• carbene 6B could not be characterized in non-complexed form. Deprotonation of 6A/B gave the anionic NHC 7. The two tautomers 6A/6B and the anionic NHC 7 could be trapped as complexes. These results supplement our knowledge about the interesting area of overlap between mesomeric betaines and N-heterocyclic

Chiral ammonium betaine-catalyzed asymmetric Mannich-type reaction of oxindoles

• Masahiro Torii,
• Kohsuke Kato,
• Daisuke Uraguchi and
• Takashi Ooi

Beilstein J. Org. Chem. 2016, 12, 2099–2103, doi:10.3762/bjoc.12.199

• 464-8602, Japan 10.3762/bjoc.12.199 Abstract A highly diastereo- and enantioselective Mannich-type reaction of 3-aryloxindoles with N-Boc aldimines was achieved under the catalysis of axially chiral ammonium betaines. This catalytic method provides a new tool for the construction of consecutive

• ][14]. Ammonium betaines are defined as intramolecular ion-pairing quaternary ammonium salts. In 2008, we employed this structurally distinct molecular scaffold for designing a novel bifunctional organic base catalyst [23], namely axially chiral ammonium betaines of type 1 (Figure 1) [24][25], and

• the scope of this mode of stereoselective Mannich-type reaction, which involve the generation of vicinal quaternary and tertiary stereocenters. Further investigations into the potential utility of ammonium betaine catalysis are underway in our laboratory. Chiral ammonium betaines. ORTEP diagram of 4ca

Fe(II)/Et₃N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

• Ekaterina E. Galenko,
• Olesya A. Tomashenko,
• Alexander F. Khlebnikov,
• Mikhail S. Novikov and
• Taras L. Panikorovskii

Beilstein J. Org. Chem. 2015, 11, 1732–1740, doi:10.3762/bjoc.11.189

• products were easily transformed into the corresponding 3-(5-methoxycarbonyl-1H-imidazol-3-ium-3-yl)pyrrol-1-ides, which in turn can be hydrolyzed under basic conditions into the corresponding betaines. A carbene tautomeric form of the 4-methoxycarbonyl-substituted imidazolylpyrrolides was trapped by

• in the equilibrium with N-heterocyclic carbenes 5 and betaine 6 (Scheme 1). Interplay between N-heterocyclic carbenes, heterocyclic betaines and ylides is currently intensively investigated as a promising route for tuning NHC for specific use. This topic was extensively reviewed [10][11][12][13][14

• (Scheme 4). Ylide 2a was hydrolyzed with a lower yield due to the high solubility of the salt 14a in water. Betaines 6 can, in principle, exist in tautomeric equilibrium with the corresponding carboxy-substituted ylides 4 and N-heterocyclic carbenes 5. The results of the DFT study of the relative

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-azabuta-1,3-dienes and/or 2H-1,4-oxazines. Keywords: 2-azabuta-1,3-dienes; azirines; diazo compounds; nitrogen ylides; 2H-1,4-oxazines

• opening to give atropoisomeric oxazinium betaines 14j,14′j and their cyclization into adducts 6j and 7j, respectively. Besides, betaines 14j,14′j can result from aziridine ring opening in azirenooxazole 10j into carbonyl ylide 15j and its addition to ketene 12 (Scheme 4). The energy profiles for both the

• the plot) which undergo a virtually barrierless aziridine ring opening to give oxazinium betaines 14j,14′j. The activation barriers to both the transformation pathways of 10j to 13 are close to each other (10.5 and 11.6 kcal/mol, respectively) but much lower than that to the ring opening of

Influence of cyclodextrin on the UCST- and LCST-behavior of poly(2-methacrylamido-caprolactam)-co-(N,N-dimethylacrylamide)

• Alexander Burkhart and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 1951–1958, doi:10.3762/bjoc.10.203

• influenced significantly by supramolecular interactions with cyclodextrin [9]. Accordingly, we described in 2003 for the first time, that the LCST of a poly(N-adamantylacrylamide-co-N’-isopropylacrylamide) is influenced by CD [10]. Furthermore, the interaction of poly(pseudo-betaines) with CD leads to an

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• indazole 3 has been generated by thermal decarboxylation of indazolium-3-carboxylates 1 [20] which belong to the class of pseudo-cross-conjugated heterocyclic mesomeric betaines (Scheme 1). Its properties have been calculated [20][21] and examined by means of vibrational spectroscopy [21]. It was shown

• that pseudo-cross-conjugated mesomeric betaines decarboxylate readily in the absence of stabilizing effects such as hydrogen bonds to protic solvents or water of crystallization [18][19]. Thus, the Gibbs free energy difference for the decarboxylation of 1,2-dimethylindazolium-3-carboxylate under

• monochloro compound was detectable. Obviously, once the dimerized species is formed under these conditions, there is no equilibrium between the free N-heterocyclic carbene I and its dimers II or III. A closer inspection of the structures reveals that the intermediary betaines III are representatives of the

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• cyclization occurs during the oxidation of 1,4-betaines 291a–d prepared from dienones 290a–d containing an azide group in the side chain. The reaction yields peroxide-bridged indolizinediones 292a–d (Scheme 82) [339]. 3.12. Structural modifications, in which 1,2-dioxane ring remains intact This section deals

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• : cyclodextrin; heterocyclic mesomeric betaine; imidazole; polymer; X-ray single-crystal analysis; Introduction Heterocyclic mesomeric betaines [1] are interesting starting materials for heterocycle and polymer synthesis due to there intriguing chemical properties. They can be broadly classified into four main

• groups, i.e., conjugated heterocyclic mesomeric betaines (CMB), which are associated with 1,3-dipoles; cross-conjugated heterocyclic mesomeric betaines (CCMB), which are associated with 1,4-dipoles; pseudo-cross-conjugated mesomeric betaines (PCCMB), which can be converted into Arduengo carbens [2][3

• ][6] or methacrylic [7][8] moieties were synthesized and polymerized by Ritter et al. Furthermore, photosensitive mesoionic main-chain polymers were also prepared [9][10]. Recently, A. Schmidt et al. described the synthesis of polymeric mesomeric betaines by quaternization of poly(4-vinylpyridine

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• theoretically. Abe et al. studied pyridinium betaines of general formula 72 consisting of negatively charged benzimidazolate and a positively charged pyridinium ion (Figure 13; [79]). Moreover, the π-conjugated system was systematically enlarged and either donor- or acceptor-substituted in order to generate D-π

• ][81], push–pull amines and betaines 74–78 [82][83][84][85][86][87], alkoxy derivatives 79,80 [88], biimidazoles 81 [89][90][91][92], and triimidazoles 82 [93][94], as well as fullerenes [95] and polymers [96][97][98][99]. The chemistry of 4,5-dicyanoimidazole was reviewed in 1987 by Donald and Webster

• betaines 72 [75][76][77][78][79]. Overview of 4,5-dicyanoimidazole derivatives investigated by Rasmussen et al. [29][81][82][83][84][85][86][87][88][89][90][91][92][93][94]. 4,5-Dicyanoimidazole-derived chromophores 84–87 [103][104][105][106]. Push–pull chromophores 88–93 with systematically extended π

Reagent controlled addition of chiral sulfur ylides to chiral aldehydes

• Varinder K. Aggarwal and
• Jie Bi

Beilstein J. Org. Chem. 2005, 1, No. 4, doi:10.1186/1860-5397-1-4

• reacted much more reversibly as evidenced by the higher trans selectivity (96: 4), the C2 control was similar (84:16) (8a+8c: 8b) to the reaction under kinetic control (Table 1, entry 2). This indicated that the rate of bond rotation or the rate of the ring closure of the two anti betaines (k5 and k7 or