1992
DOI: 10.1002/cber.19921250912
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(E,Z)‐Gleichgewichte, 15. Synthesen und erhöhte Konfigurationslabilität von 2‐Iminoindan‐Derivaten mit Vorderseitenspannung

Abstract: (EZ) Equilibria, 15111. -Syntheses and Lability of the Configuration of 2-Iminoindan Derivatives with Front StrainSyntheses and properties are described for sterically shielded imines R,C=NR (3c, e, g-k), which are rather inert toward nucleophiles. Nucleophilic attack a t the nitrogen atom of 3k is indicated by the formation of the azine 4. (E,Z) Configurational diastereotopomerization (antilsyn) is strongly dependent on N substituents [CH3, phenyl, I-naphthyl, acetyl, Si(CH3)3, cyano, SC6HJ, SOC6H5, S02C6H5, … Show more

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Cited by 16 publications
(7 citation statements)
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“…This resulted through intramolecular repulsive interactions by the 1,1,3,3‐tetramethyl substituents (energetic elevation of the ground state) and was also perceptible by the bigger barrier reduction from 16.3 kcal mol −1 (entry 8) in α‐(2,6‐dimethylphenyl)vinyllithium ( 4 ) to 13.35 kcal mol −1 for 7 a (entry 1). A comparable inversion‐accelerating effect (3–5 kcal mol −1 ) of the bulky 1,1,3,3‐tetramethyl armament had previously been noted with N ‐phenyl imines that are sterically equivalent and isoelectronic models of the inverting carbanionic moieties in 4 and 7 a . Therefore, it became necessary to avoid the accelerating front strain in 7 a , b and to use barriers of the less encumbered vinyllithiums such as 4 as references for the wanted substituent effects at the α‐aryl groups.…”
Section: Resultsmentioning
confidence: 99%
See 1 more Smart Citation
“…This resulted through intramolecular repulsive interactions by the 1,1,3,3‐tetramethyl substituents (energetic elevation of the ground state) and was also perceptible by the bigger barrier reduction from 16.3 kcal mol −1 (entry 8) in α‐(2,6‐dimethylphenyl)vinyllithium ( 4 ) to 13.35 kcal mol −1 for 7 a (entry 1). A comparable inversion‐accelerating effect (3–5 kcal mol −1 ) of the bulky 1,1,3,3‐tetramethyl armament had previously been noted with N ‐phenyl imines that are sterically equivalent and isoelectronic models of the inverting carbanionic moieties in 4 and 7 a . Therefore, it became necessary to avoid the accelerating front strain in 7 a , b and to use barriers of the less encumbered vinyllithiums such as 4 as references for the wanted substituent effects at the α‐aryl groups.…”
Section: Resultsmentioning
confidence: 99%
“…This resulted through intramolecular repulsive interactions [1] by the 1,1,3,3-tetramethyl substituents (energetic elevation of the ground state) and was also perceptible by the bigger barrier reduction from 16.3 kcal mol À1 (entry 8) in a-(2,6dimethylphenyl)vinyllithium (4)t o1 3.35 kcal mol À1 for 7a (entry 1). Ac omparable inversion-accelerating effect (3-5 kcal mol À1 )o ftheb ulky 1,1,3,3-tetramethyl armament had previously [18] been noted with N-phenyl imines that are sterically equivalent and isoelectronic modelso ft he inverting carbanionic moieties in 4 and 7a.T herefore, it became necessary to avoid the accelerating fronts train in 7a,b and to use barriers of the less encumberedv inyllithiumss uch as 4 as references for the wanted substituent effects at the a-aryl groups.T his choice restricted our NMR-based rate measurements to the cis and trans b-H atoms that are constitutionally equivalent but stereochemically different (namely," diastereotopic"): With increasingly rapid cis/trans interconversion ("diastereotopomeri- zation"), the four absorption lines of this H 2 C=C 1 HNMR spectrum will first suffer increasing line broadening and then "coalesce" into as inglet at the averagedr esonancep osition of (d cis + d trans )/2. [19] Computer-aided simulations [20] of these ratedependentl ine shapes can furnish the pseudo-first-order rate constants k y of the pseudomonomolecular( namely,T HF-catalyzed) cis/trans stereoinversion.…”
Section: On the P-routementioning
confidence: 95%
“…Fast rotation at the N6′C7′ bond could confer pairwise identity to the methyl groups in the Southern indane. However, an elegant DNMR study of 2,2,5,5‐tetramethylcyclopentylidene N‐arylimines, a related model system, by Knorr et al14 established N‐inversion (lateral shift). In the case of 13 , N ‐ inversion would lead to a cis ‐2‐azabutadiene which should provide a second set of non‐equivalent methyl groups.…”
Section: Resultsmentioning
confidence: 99%
“…The free bases 4LZ61, 6 [391,7[391,8r3' 1,9L4OI,12c2' 1,13Iz9l were used directly, while 5 was also weighed as its hydrochloride[z61 and 11 as its hydrogen perchl~rate[~~I.…”
Section: Compoundsmentioning
confidence: 99%