Ringtransformationen heterocyclischer Verbindungen. XII. Neuartige Spiroindoline via Ringtransformation von 2,4,6-Triaryl-pyryliumsalzen mit 2-Methylen-indolinen

Abstract

Ring Transformations of Heterocyclic Compounds. XII. Novel Spiroindolines via Ring Transformation of 2,4,6‐Triarylpyrylium Salts with 2‐Methyleneindolines 2,4,6‐Triarylpyrylium salts 1 react with 2‐methyleneindolines 2 or their salts 2 HX in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C4 + C2] pyrylium ring transformation to give diastereomerically pure 6‐aroyl‐3,5‐diaryl‐spiro[cyclohexa‐2,4‐diene‐1,2′‐indolines] 3, which represent a novel type of spiroindoline compounds. When the 1′‐phenyl substituted spiroindolines 3 (RPh, R′H) are treated with p‐toluenesulfonic acid in chloroform the 4,6‐diaryl‐2‐[1‐methyl‐1‐(2‐phenylaminophenyl)methyl]benzophenones 4 are obtained as the result of an intramolecular amine elimination. Structural elucidation of the reaction products 3/4 is based on spectroscopic data and on an X‐ray determination of the bis(4‐bromophenyl) substituted spiroindoline 3i.

The Enantiomers of Spiro(cyclohexadiene-indolines) and their Thermal Racemization

“…The synthesis of the spiro(cyclohexadiene-indolines) 4a±n has been described in a previous paper [2].…”

“…In 1995, a novel type of spiroindolines in which the second heterocyclic ring is replaced by a carbocycle, has been described [2]. These spiro(cyclohexadieneindolines) 4 have been obtained by diastereoselective ring transformation of the pyrylium salts 1 with 3,3-dimethyl-2-methylene-indolines 2 (Fischer base and derivatives thereof ).…”

Ring transformations of heterocyclic compounds. XXV. Phenanthrene aldehyde imines via ring transformation of pyrylium salts with methylenedihydroisoquinolines—A novel access to the phenanthrene skeleton

“…A high solvent polarity [19] seems to be necessary for the stabilization of the betaine intermediates 9. Hence, on replacing the methanol by the less polar ethanol the merocyanines are not cyclized to 9 but undergo an electrocyclic reaction to the spiro derivatives 10 which are related to spiro[cyclohexadiene-indolines] and spiro-[cyclohexadiene-dihydroacridines], the transformation products of the pyrylium salts 1 with methyleneindolines and methylenedihydroacridines, respectively [1,[4][5][6][7]. An intramolecular amine elimination converts 10 into the benzophenones 11, the same type of compounds as obtained by the reaction of the salts 1 with methylenedihydrobenzoxazoles as final products [10].…”

“…The first type is characterized by the formation of a cyclohexadiene ring from four of the five carbon atoms of the pyrylium moiety and two C-atoms of the nucleophile. It has been observed in the reaction of the salts 1 with methyleneindolines [1,4], their spiroconnected [5] and benzo-fused [6] derivatives and with methylenedihydroacridines [7] giving rise to spiro-[cyclohexadiene-indolines] and spiro[cyclohexadienedihydroacridines], respectively, which represent first examples of a novel class of photochromic compounds, the spiro[cyclohexadiene-azaheterocycles] [8,9]. The transformation of the salts 1 with methylenedihydrobenzoxazoles to aryl substituted aminobenzophenones is the only known example for the second type, in which instead of a cyclohexadiene a benzene ring is built up [10].…”

Ring transformations of heterocyclic compounds. XXIV. 1′,2′,5′,6′‐Tetrahydro‐4′H‐spiro[cyclohexa‐2,4‐diene‐1,2′‐pyrrolo[3,2,1‐ij]quinoline] and 1,2,4,5,6,7‐hexahydrospiro[azepino[3,2,1‐hi]indole‐2,1′‐cyclohexa[2,4]diene] – Two new spiro[cyclohexadiene‐azaheterocycles] easily accessible by pyrylium ring transformation

“…Whereas the reaction of the pyrylium salts 1 with the 2-methylene-1,2,4,5-tetrahydropyrrolo[3,2,1-hi]indole 3a (n = 2), generated in situ from the 4-methyl-2,5-dihydro-1H-pyrrolo[3,2,1-hi]indolium perchlorate 2a, failed, the salts 1 react with the 2-methylene-1,2,5,6-tetrahydro-4H-pyrrolo[3,2,1-ij]quinolines 3b,c (n = 3) and the 2-methylene-1,2,4,5,6,7-hexahydroazepino[3,2,1-hi]indole 3d (n = 4), obtained in situ from the corresponding 2-methyl-1,4,5,6-tetrahydropyrrolo[3,2,1-i f]quinolinium perchlorates 2 b,c and the 2-methyl-4,5,6,7-tetrahydro-1H-azepino[3,2,1-hi]indolium perchlorate 2d, in the presence of triethylamine/acetic acid in boiling ethanol by a 2,5-[C 4 + C 2 ] transformation in high yield and diastereoselectivity to give the 1 ' , 2 ' , 5 ' , 6 ' -t e t r a h y d r o-4 'H-s p i r o [ c y c l o h e x a -2 , 4 -d i e n e -1 , 2 ' -p y r r o l o [ 3 , 2 , 1 -i j]quinolines] 5 and the 1,2,4,5,6,7h e x a h y d r o s p i r o [ a z e p i n o [ 3 , 2 , 1 -h i]indole-2,1'-cyclohexa [2,4]dienes] 6, respectively. The influence of the length of the (CH 2 ) n chain in 3 on the product formation and the diastereoselectivity can be explained by differences of the steric strain in the spiro compounds.…”