Indolenine derivatives

The condensation of a vinylogous formamide with an enamine has been applied to an aza azulene synthesis (351). The point of attachment of the aldehyde to the enamine in condensations with indolenin derived poly-enamines was found to favor the second double bond (352,353). 

The reduction of 2-methyl-1,2,3,4-tetrahydro-y-carboline (92) with zinc and hydrochloric acid in the presence of mercuric chloride gives the indolenine derivative, 2-methyl-l,2,3,4,4a,9b-hexahydro-y-carbo-line (93). A related compound, 4,9b-diethyl-2-methyl-l,2,3,4,4a,9b-hexahydro-y-carboline (96), was obtained by catalytic hydrogenation of 95, which was prepared by Fischer ring closure of the phenyl-hydrazone 94. The stereochemistry of the B/C ring junction in these... 

Most of the substitution reactions of di-, tetra, and hexa-hydro-carbolines and of their oxo derivatives are similar to those of the parent indole or indolenine derivatives. Nitration and bromination of harma-line (l-methyl-3,4-dihydro-j8-carbolme) are referred to in Section IV, A, 1. Sulfonation and azO COupling ° proceed as expected for indole derivatives. The preparation of chlorinated and iodinated derivatives of 6-nitroharmaline has been reported,but their structures have not been established. 

A series of oxidative rearrangements of tetrahydro-j8-carbolines may be rationalized on the basis of a general reaction of 2,3-disub-stituted indoles which was recently recognized by Taylor. Attack at the 4a-position of the tetrahydrocarboline (341) by an electrophile yields the indolenine derivative 342, which is in equilibrium with the isomeric species 342a. Compounds of structure 342 and 342a can undergo a variety of reactions leading to different products. 

An instance of the pyrolytic ring cleavage of a quaternary 1,2-dihydro-y-carbolinium salt to an indolenine derivative has been reported. ... 

The position 3 is so much preferred in electrophilic substitution, that it is the site for primary attack even when it is already substituted. Jackson and co-workers255 have provided a considerable body of evidence that electrophilic substitution at the 2-position of 3-substituted indoles is an indirect process involving prior attack at the 3-position to give an indolenine derivative (30), which subsequently rearranges to a 2,3-disubstituted indole. 

Cabucine (10-methoxyajmalicine) (135) and tetraphylline (11-methoxyaj-malicine) (136) have been converted into the corresponding oxindole A and B analogues (137-140) via the corresponding 7-chloro-indolenine derivatives.82... 

The reaction of yohimbine hydrochloride with m-chloroperbenzoic acid also results in the formation of a 7-chloro-indolenine derivative hence the product, following normal Ab-oxidation, is the JVb-oxide (141). In contrast to the 7-chloro-indolenine derivatives, no conversion into the corresponding oxindole analogue... 

Oxidation of tabersonine hydrochloride with m-chloroperbenzoic acid does not give a 16-hydroxy-derivative, as expected, but a 16-chloro-indolenine derivative (201), presumably via the generation of Cl+ from chloride ion and the oxidant in the presence of an excess of oxidant, the Nh-oxide of (201) is formed.83... 

A considerable amount of attention has been devoted to the total or partial synthesis of alkaloids in this group during the past year. The application of 3-halogeno-indolenine derivatives of alkaloids in synthesis is the subject of a review.49... 

Again, this is an interesting model for a possible way of adsorbing and hydrogenating indoles on solid catalysts at the early stages of HDN. Ti (N)-Indolyl complexes are activated toward protonation at the P-carbon atom, which transforms them into r (N)-indolenine derivatives (See e.g. Eq. 6.7) [33]. 

Dimethylindole (14) and 2,3,3-trimethylindolenine (15) were obtained by the action of methyl iodide on 2-methylindole magnesium iodide.The trisubstituted indolenine derivative 15 was also formed in good yield in a similar manner from 2,3-dimethylindole magnesium iodide.Nakazaki and his co-workers have described the preparation of a number of 2,3,3-trisubstituted indolenines, including 2,3,3-trimethylindolenine (15), 2,3-dimethyl-3-isopropyl-indolenine (16), and 2,3-dimethyl-3-[Pg.49]

Hoshino and his co-workers reported that treatment of the Grignard reagent obtained from tryptamine (23), by the action of a suitable alkyl magnesium halide, with methyl iodide in benzene did not give the expected indolenine derivative 24 instead dinordeoxyeseroline... 

In their synthesis of ( )-perophoramidine, Funk and Fuchs [27] use the base-mediated reaction of a 3-siloxyalkyl-substituted indole with a 3-bromoindolin-2-one to produce an indolenine derivative as a key step. The formation and subsequent IDA cycloaddition of an indole-2-one derivative followed by ring opening of the cycloadduct is proposed as one possible mechanism for the above reaction. A similar approach was also used by Dalko and coworkers in the total synthesis of the bis-pyrroloindoline alkaloid ( )-A b-desmethyl-/ncso-chimonanthine [28]. 

Startg. indolenine derivative refluxed 6% hrs. in tetralin -> indole derivate. Y S9%. F. e., also pyrazoles from isopyrazoles, s. R. K. Bramley and R. Grigg, Chem. Commun. 1969, 99. 

Photochemically labile protecting groups have also been known for several years newly described indolenine derivatives (24) of acids give back the acid when photolysed in water, but give the amide in the presence of ammonia. There has been a review of the electrochemical removal of protecting groups. ... 

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