Stable Ion NMR and GIAO-DFT Study of Novel Cations from 8,16-Dicyano[2.2]metacyclophanedienes and from Strategically Substituted/Benzannelated Dihydropyrenes: Charge-Induced Tropicity Modulation and π-Switching
摘要:
[GRAPHICS]The dicyanometacyclophanediene 1 is diprotonated at the cyano groups (1H(2)(2+)) in various superacid media. Upon quenching, intact 1 and the ring-closed CPD 2 were obtained in a 3:2 or 3:1 ratio, depending on the superacid system. Compound 2 undergoes ring opening in the superacid to give the ipso-monoprotonated 2H(+), which on quenching furnishes 1-cyanopyrene as a major product together with 2 and 1. The dication 3(2+), with strongly deshielded internal methyls, was generated from the epoxyannulene 3. Ketones 4-6 and ester 7 are O/C diprotonated to give paratropic carboxonium-annulenium dications (4H(2)(2+), 5H(2)(2+), 6H(2)(2+), and -7H(2)(2+), respectively). Ester 8 gives a trication by two-electron oxidation and O-protonation. Conjugated carboxylic acid 9 gives a mixture of two dications by CO and ring protonation. The dibromo derivatives 10 and 11 form carboxoniurn ions, whereas the monobromo derivative 12 is O/C diprotonated to give an oxonium-annulenium dication. Charge delocalization modes and tropicity in the resulting species are evaluated by NMR and GIAO-DFT. Facile formation of 2 from I in quenching experiments indicates that thermal closing can be achieved with the diprotonated dinitrile, without imposing skeletal rearrangement.
Stable Ion NMR and GIAO-DFT Study of Novel Cations from 8,16-Dicyano[2.2]metacyclophanedienes and from Strategically Substituted/Benzannelated Dihydropyrenes: Charge-Induced Tropicity Modulation and π-Switching
摘要:
[GRAPHICS]The dicyanometacyclophanediene 1 is diprotonated at the cyano groups (1H(2)(2+)) in various superacid media. Upon quenching, intact 1 and the ring-closed CPD 2 were obtained in a 3:2 or 3:1 ratio, depending on the superacid system. Compound 2 undergoes ring opening in the superacid to give the ipso-monoprotonated 2H(+), which on quenching furnishes 1-cyanopyrene as a major product together with 2 and 1. The dication 3(2+), with strongly deshielded internal methyls, was generated from the epoxyannulene 3. Ketones 4-6 and ester 7 are O/C diprotonated to give paratropic carboxonium-annulenium dications (4H(2)(2+), 5H(2)(2+), 6H(2)(2+), and -7H(2)(2+), respectively). Ester 8 gives a trication by two-electron oxidation and O-protonation. Conjugated carboxylic acid 9 gives a mixture of two dications by CO and ring protonation. The dibromo derivatives 10 and 11 form carboxoniurn ions, whereas the monobromo derivative 12 is O/C diprotonated to give an oxonium-annulenium dication. Charge delocalization modes and tropicity in the resulting species are evaluated by NMR and GIAO-DFT. Facile formation of 2 from I in quenching experiments indicates that thermal closing can be achieved with the diprotonated dinitrile, without imposing skeletal rearrangement.
Stable Ion NMR and GIAO-DFT Study of Novel Cations from 8,16-Dicyano[2.2]metacyclophanedienes and from Strategically Substituted/Benzannelated Dihydropyrenes: Charge-Induced Tropicity Modulation and π-Switching
作者:Kenneth K. Laali、Takao Okazaki、Reginald H. Mitchell、Khurshid Ayub、Rui Zhang、Stephen G. Robinson
DOI:10.1021/jo701932j
日期:2008.1.1
[GRAPHICS]The dicyanometacyclophanediene 1 is diprotonated at the cyano groups (1H(2)(2+)) in various superacid media. Upon quenching, intact 1 and the ring-closed CPD 2 were obtained in a 3:2 or 3:1 ratio, depending on the superacid system. Compound 2 undergoes ring opening in the superacid to give the ipso-monoprotonated 2H(+), which on quenching furnishes 1-cyanopyrene as a major product together with 2 and 1. The dication 3(2+), with strongly deshielded internal methyls, was generated from the epoxyannulene 3. Ketones 4-6 and ester 7 are O/C diprotonated to give paratropic carboxonium-annulenium dications (4H(2)(2+), 5H(2)(2+), 6H(2)(2+), and -7H(2)(2+), respectively). Ester 8 gives a trication by two-electron oxidation and O-protonation. Conjugated carboxylic acid 9 gives a mixture of two dications by CO and ring protonation. The dibromo derivatives 10 and 11 form carboxoniurn ions, whereas the monobromo derivative 12 is O/C diprotonated to give an oxonium-annulenium dication. Charge delocalization modes and tropicity in the resulting species are evaluated by NMR and GIAO-DFT. Facile formation of 2 from I in quenching experiments indicates that thermal closing can be achieved with the diprotonated dinitrile, without imposing skeletal rearrangement.