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A product formed in the autoxidation of 2,3-dimethylindole and in the dimerization of 2,3-dimethyl-3-hydroxy-3H-indole has been identified as 3,3a,4,8b-tetrahydro-3′,3a,8b-trimethylsopiro-[2H-furo[3,2-b]indole-2,2′-indoline]-3′-ol (V), on the basis of u.v., i.r., n.m.r., mass spectral, and chemical evidence. Several reactions of (V). involving reduction, cleavage, and rearrangements to pyrrolo[1,2-a:5,4-b′]di-indole derivatives are presented.

Indole derivatives with a free position 3 are converted by benzoyl nitrate into the corresponding 3-nitro-derivatives. Under the same conditions, 3-methylindole gives 3-methyl-2-nitroindole, and 2,3-diphenylindole yields a mixture containing 3,3-diphenyloxindole and 6-nitro-2,3-diphenylindole. 2,3-Dimethylindole is oxidized by benzoyl nitrate to 3-methylindole-2-carbaldehyde, and under somewhat different conditions to two compounds, which, on the basis of spectral and chemical evidence, are identified as 5a,10b,12-trimethyl-5a,6,10b,11-tetrahydropyrrolo[1,2-a:5,4-b′]di-indole and the corresponding 6-nitroso-derivative. 3-Ethyl- and 3-phenyl-2-methylindole give similar products.

Boron trifluoride–ether complex in benzene rapidly converts (–)(S,S)-1,2-epoxy-1-phenylcyclohexane and the corresponding (–)-(S,S)-cis-1,2-diol and (+)-(R,S)-trans-1,2-diol into mixtures of 1-phenylcyclopentanecarbaldehyde and (–)-(S)-2-phenylcyclohexanone, while a slower secondary reaction transforms the aldehyde into the ketone. (–)-(S,S)-cis-2-Fluoro-2-phenylcyclohexanol, quantitatively formed from the epoxide with boron trifluoride–ether, is converted by the same reagent in benzene into the aldehyde and ketone. All the primary conversions into the ketone take place with a high optical yield, as expected for 1,2-hydride shifts. The large differences in the ketone–aldehyde ratios can be explained by assuming that, while the diols and fluorohydrin rearrange through open carbonium ions, the epoxide–aldehyde conversion takes place in a more concerted manner. A comparison with previous data on the same reaction applied to the corresponding diastereoisomeric 4-t-butyl derivatives strongly suggests that the diols and fluorohydrin react preferentially in their less stable conformations with an axial phenyl group.

The two diastereoisomeric 1,2-epoxy-1-phenyl-4-t-butylcyclohexanes and the corresponding four diols are converted into mixtures of 2-phenyl-5-t-butylcyclohexanones and 1-phenyl-3-t-butylcyclopentanecarbaldehydes by boron trifluoride–ether complex. The steric course of these reactions is interpreted in terms of a mechanism involving open carbonium ion intermediates for the diols, whereas the rearrangement of the epoxides appears to be more concerted. The silver oxide-promoted rearrangements of the cis-chlorohydrins of the same series seem to be entirely concerted.