3,4-Diazanorcaradienes and 4,5-dihydropyridazines as precursors for new stable azomethine ylides

Böhm, Thomas; Elender, Kurt; Riebel, Peter; Troll, T.; Weber, Andreas; Sauer, Jürgen

doi:10.1016/s0040-4020(99)00516-5

Cited by 8 publications

(2 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The stable dicyanoazomethine ylides 257, derived from reaction of 3,4-diazanorcaradienes 255 with tetracyanoethylene oxide 256 [148], undergo reaction with a range of dipolarophiles [149]. The carbonyl dipolarophile trichloroacetaldehyde (2g) undergoes efficient cycloaddition with ylide 257 to give cycloadduct 258 isolated as a single endo stereoisomer in 40% yield (Scheme 75).…”

Section: Reactions Of Dicyanoazomethine Ylidesmentioning

confidence: 99%

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

Meyer

Ryan

2016

Molecules

View full text Add to dashboard Cite

Abstract:We provide a comprehensive account of the 1,3-dipolar cycloaddition reactions of azomethine ylides with carbonyl dipolarophiles. Many different azomethine ylides have been studied, including stabilized and non-stabilized ylides. Of the carbonyl dipolarophiles, aldehydes including formaldehyde are the most studied, although there are now examples of cycloadditions with ketones, ketenes and carboxyl systems, in particular isatoic anhydrides and phthalic anhydrides. Intramolecular cycloadditions with esters can also occur under certain circumstances. The oxazolidine cycloadducts undergo a range of reactions triggered by the ring-opening of the oxazolidine ring system.

show abstract

Section: Reactions Of Dicyanoazomethine Ylidesmentioning

confidence: 99%

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

Meyer

Ryan

2016

Molecules

View full text Add to dashboard Cite

show abstract

“…Although numerous investigations have been concerned with the effects of substituents on these systems, usually with the aim of lowering the energy barriers towards degenerate Cope rearrangements,6 relatively few aza analogues have been studied experimentally7 even though the effects of aza substitution at different positions were predicted quite early on 8. In fact, three types of aza‐3,4‐homotropilidenes have been reported, namely 7‐aza‐3,4‐homotropilidenes,9 in which aza‐substitution does not involve the Cope system, and 1,6‐diaza‐10 and 1,7‐diaza‐3,4‐homotropilidenes,11 the hypothetical Cope rearrangements of which would lead to much less stable isomers. The lack of degenerate aza‐homotropilidenes comes as no surprise as the hypothetical members 1b contain the 2,3‐dihydro‐6 H ‐1,4‐diazepine moiety 2 ,12 a notoriously unstable system that readily tautomerizes to the conjugated 1 H isomer 3 13.…”

Section: Introductionmentioning

confidence: 99%

2,2′‐Bis‐azonia‐Cope Rearrangements of 2,3‐Homo‐6H‐1,4‐diazepinium Dications

2013

View full text Add to dashboard Cite

The condensation of cis‐1,2‐cyclopropanediamines with 1,3‐dicarbonyl compounds and 1,5‐diazapentadienium salts afforded 2,3‐homo‐1H‐1,4‐diazepinium salts, which were protonated by very strong acids to yield 2,3‐homo‐6H‐1,4‐diazepinium dications. As measures of basicity, the mole fractions of water in trifluoromethanesulfonic acid at half‐protonation were determined for 2,3‐homo‐ and 2,3‐dihydro‐1H‐1,4‐diazepinium salts. 2,3‐Homo‐6H‐1,4‐diazepinium dications underwent 2,2′‐bis‐azonia‐Cope rearrangements, as can be inferred from the product structures, or H/D exchange involving the methylene group of the cyclopropane rings. Apparently, in the Cope rearrangement, this group is interchanged with the methylene group in the seven‐membered ring (C‐6), which is susceptible to H/D exchange in strong deuteriated acids. Rapid, degenerate, as well as very slow, strongly biased Cope rearrangements have been uncovered in this way. 1H NMR spectra, recorded at elevated temperatures for a solution of the parent dication in trifluoromethanesulfonic acid, reveal broadening of the interchanging 2‐H, 3‐H and 5‐H, 7‐H signals and eventually the onset of their coalescence. Surprisingly, the estimated free enthalpy of activation is higher (ΔG‡110 °C ≈ 73 ± 2 kJ/mol) than that of 3,4‐homotropilidene (ΔG‡110 °C = 61 kJ/mol), not lower, as would be expected on the basis of the well‐known charge‐acceleration of Cope rearrangements.

show abstract

ChemInform Abstract: 3,4‐Diazanorcaradienes and 4,5‐Dihydropyridazines as Precursors for New Stable Azomethine Ylides.

et al. 1999

View full text Add to dashboard Cite

show abstract

3,4-Diazanorcaradienes and 4,5-dihydropyridazines as precursors for new stable azomethine ylides

Cited by 8 publications

References 5 publications

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

2,2′‐Bis‐azonia‐Cope Rearrangements of 2,3‐Homo‐6H‐1,4‐diazepinium Dications

ChemInform Abstract: 3,4‐Diazanorcaradienes and 4,5‐Dihydropyridazines as Precursors for New Stable Azomethine Ylides.

Contact Info

Product

Resources

About