220466-11-5Relevant academic research and scientific papers
Triflic acid-promoted cycloisomerization of 2-alkynylphenyl isothiocyanates and isocyanates: A novel synthetic method for a variety of indole derivatives
Saito, Takao,Sonoki, Yoshihiko,Otani, Takashi,Kutsumura, Noriki
supporting information, p. 8398 - 8407 (2014/12/10)
A new approach towards the synthesis of indole derivatives via triflic acid-promoted cycloisomerization with rearrangement of 2-(alkyn-1-yl)phenyl isothiocyanates and 2-(alkyn-1-yl)phenyl isocyanates has been achieved. By this methodology, structurally di
Biradicals/zwitterions from thermolysis of enyne-isocyanates. Application to the synthesis of 2(1H)-pyridones, benzofuro[3,2-c]pyridin-1(2H)-ones, 2,5-dihydro-1H-pyrido[4,3,-b]indol-1-ones, and related compounds
Li, Hongbin,Yang, Hua,Petersen, Jeffrey L.,Wang, Kung K.
, p. 4500 - 4508 (2007/10/03)
Thermolysis of benzannulated enyne-isocyanates 13 and enyne-isocyanates 36 and 37 promoted the cycloaromatization reactions to generate in situ O,4-didehydro-2-hydroxyquinolines and O,4-didehydro-2-hydroxypyridines, respectively, as reactive intermediates. These cycloaromatized intermediates could be captured either as biradicals and/or as zwitterions depending on the nature of the substituent at the alkynyl terminus. The intermediate derived from cycloaromatization of 13a bearing a phenyl substituent could be regarded as biradical 14, which then abstracts hydrogen atoms from γ-terpinene leading to 2(1H)-quinolinone 15. Alternatively, the same intermediate could also be regarded as zwitterion 14′, which then undergoes an initial hydride abstraction from γ-terpinene followed by protonation to produce 15. The presence of a 2-phenylethyl substituent in 13b and 37a or a 2-methylphenyl substituent in 37b also allowed the resulting intermediates to be captured intramolecularly either as biradicals or as zwitterions, producing 2(1H)-quinolinone 19, 2(1H)-pyridone 39, and benzopyranopyridine 43, respectively. On the other hand, with a 2-methoxyphenyl, a 2-(dimethylamino) phenyl, or a 3-methoxypropyl substituent, the chemical behavior of the cycloaromatized adduct could be best accounted for in terms of a zwitterionic intermediate leading to benzofuro [3,2-c]quinolin-6(5H)-one (20), 5,11-dihydro-11-methyl-6H-indolo-[3,2-c]quinolin-6-one (25), benzofuro[3,2-c]pyridin-1(2H)-one 44, 2,5-dihydro-2,5-dimethyl-1H-pyrido-[4,3-b] indol-1-one 46, and related compounds. Interestingly, thermolysis of 37f bearing a 2-(methoxymethyl)phenyl substituent at the alkynyl terminus produced the unexpected benzopyranopyridine 56 as the major product in a process involving the cleavage of the bond between the methoxyl oxygen and the adjacent methylene carbon. The efficiency and selectivity of the cycloaromatization reaction could also be enhanced by the introduction of 1.1 to 10 equiv of dimethylphenylsilyl chloride to the reaction mixture to capture the resulting zwitterion.
Synthesis of 6H-indolo[2,3-b][1,6]naphthyridines and related compounds as the 5-aza analogues of ellipticine alkaloids
Zhang,Shi,Zhang,Wang
, p. 7977 - 7983 (2007/10/03)
Treatment of 2-(1-alkynyl)phenyl isocyanates 6 with the iminophosphorane 14 produced in situ the benzoenynyl carbodiimides 15. Thermolysis of 15 under refluxing p-xylene furnished the 6H-indolo[2,3-b][1,6]naphthyridines 5, which could be regarded as the 5-aza analogues of ellipticine alkaloids. Similarly, condensation of 6 with the iminophosphorane 20 led to the formation of the 6H-indolo[2,3-b][1,5]naphthyridines 25 as the major isomer and the 10H-indolo[2,3-b][1,7]naphthyridines 26 as the minor isomer. The indolonaphthyridines 32, 33, and 34 having a methoxyl substituent were likewise synthesized. Treatment of the diisocyanate 43 with 2 equiv of the iminophosphorane 7 furnished 45 having two indoloquinoline units incorporated in a seven-fused-ring system.
Biradicals from thermolysis of N-[2-(1-alkynyl)phenyl]-N'- phenylcarbodiimides and their subsequent transformations to 6H-indolo[2,3- b]quinolines
Shi, Chongsheng,Zhang, Quan,Wang, Kung K.
, p. 925 - 932 (2007/10/03)
Thermolysis of the carbodiimide 9a in γ-terpinene at 138 °C produced 2-(phenylamino)quinoline (11a, 49%) and the parent 6H-indolo[2,3-b]quinoline (14a, 16%). Apparently, 11a was produced via the biradical 10a followed by hydrogen-atom abstraction from γ-terpinene. A two-step biradical pathway through 12a or a one-step intramolecular Diels-Alder reaction could furnish 13a, which then underwent tautomerization to give 14a. With the carbodiimide 9b having a trimethylsilyl substituent at the acetylenic terminus, thermolysis in refluxing p-xylene at 138 °C produced the 6H-indolo[2,3- b]quinoline 14b (86%) exclusively. Treatment of 14b with 6 N NaOH in refluxing ethanol then furnished 14a in 92% yield. Similarly, the 6H- indolo[2,3-b]quinolines 14c-f were obtained from thermolysis of the carbodiimides 9c-f. The use of the aza-Wittig reaction between 4- methoxyphenyl isocyanate and the iminophosphoranes 2d and 2f to produce the corresponding carbodiimides followed by thermolysis furnished the 6H- indolo[2,3-b]quinolines 16d and 16f having a methoxy substituent at the C-2 position. Thermolysis of the carbodiimides 25a and 25b produced 26a and 26b having two indoloquinoline units connected at the 11 and 11' positions with either a three-carbon or a five-carbon tether. Using 1,4-phenylene diisocyanate for the aza-Wittig reaction with 2 equiv of the iminophosphorane 2g followed by thermolysis furnished 31 (66%) having two indoloquinoline units incorporated in the seven fused rings.
