RING-CHAIN ISOMERISM OF 1,3,3-TRIMETHYL-2-FORMYLMETHYLENE- INDOLINE (FISCHER ALDEHYDE) OXIME AND ASSOCIATED REACTIONS A. A. Tolmachev, L. N. Babichenko, I. V. Komarov, S. V. Sereda, and A. K. Sheinkman The compound 1,3,3-trimethyl-2-formylmethyleneindoline oxime is synthesized for the first time. Using the polynuclear resonance method it is shown that the oxime exists as two isomers, one of which has a cyclic structure. A number of reactions are carried out involving the carbocyclic and oxime parts of the molecule. Ring-chain isomerism in the spirochromene derivatives of 1,3,3-trialkyl-2-methyleneindoline (Fischer base) gives rise to the wide range of photochromic, thermochromic, halochromic, and solvatochromic properties that they exhibit [ 1, 2]. Studies have been made of ring-chain isomerism in Fischer base derivatives containing phenol, thiophenol, amide, and amine group substituents [ 1-4]. The ability of 1,3,3-trialkyl-2-methyleneindolines having an oxime group to demonstrate ring-chain isomerism has not been investigated [5]. Moreover, no information exists on the Fischer aldehyde oxime. When aldehyde I reacts with hydroxylamine hydrochloride, the Fischer aldehyde oxime is formed. This proved to be capable of existing in two forms: the cyclic (compound II) and acyclic (compound III) isomers. The characteristic hydroxyl group absorption band (2500-3600 cm -1) is absent from the IR spectrum of compound II. The PMR spectrum shows a CH 2 group signal which, as a result of diastereotopicity, appears as two doublets (system AB: (5 A = 2.98; 8B = 3.16 ppm; JAB = 20 Hz). Each component of these doublets is cleaved by the neighboring CH=N group with coupling constant of 2 Hz. The CH=N proton signal overlaps the aromatic proton signals. The chemical shifts of the geminal methyl group protons appear as two singlets at 1.21 and 1.32 ppm. These methyl groups also appear as two signals in the 13C NMR spectrum (27.3 and 28.1 ppm). Both these facts indicate that the molecule's asymmetry center is located nearby. The most significant pointer, however, is the chemical shift of the C(2) atom (111 ppm), which concords with data for similar spiro compounds [5]. The structure of compound II is also substantiated by a PMR spectrum taken in the presence of a Lanthanide Shift Reagent (LSR), in this case Eu(fod)3. The LSR would be expected to produce the largest weak field shift for the CH--N proton group signal, since the europium chelate coordination in this compound should occur at the nitrogen atom of the dihydroisoxazole cycle [6]. Indeed, in PMR spectra taken with varying LSR concentrations the biggest displacement into the weak field region is observed for the CH=N proton signal, which exhibits a specific Lanthanide Induced Shift (LIS) of 5.1 ppm. Extrapolation of this shift to zero LSR concentration indicates that its original position in the spectrum is 7.0 pprn. The CH 2 group proton signals also experience an appreciable induced shift (specific LIS of 3.0 and 3.4 ppm). The specific LIS for the C(3)--(CH3) 2 group is 1.1 ppm and that for the N--CH 3 group 1.5 ppm. The spectral data given above suggest that the molecule has a chiral center and a relatively stable dihydroisoxazole cycle. This enabled us to carry out selective bromination and azo coupling at position 5 of the carbocyclic ring of compound II. Similar electrophilic substitution reactions for the indoline series spiro compounds have been described in [7]. The structures of compounds IV and V are corroborated by PMR spectra. In the PMR spectra of compounds IV and V the geminal methyl and CH 2 group signals relating to chemical shift and type of cleavage are similar to those described above for compound II. When bromine and p-nitrophenyldiazo groups are introduced into the carbocyclic ring, the 5-H proton signal disappears (in compound II it is seen at 6.83 ppm), and the 7-H proton appears as a strong field doublet at 6.36 ppm 06,7 = 8.0 Hz) for compound IV and 6.64 ppm ('16,7 = 8.2 Hz) for compound V. The cyclic structure of the azo dye is also suggested by the fact that when it is dissolved in mineral acids, the absorption maximum in the UV spectrum changes from 435 to 595 nm (a batochromic shift of 160 nm). This is undoubtedly due to the fact that the isoxazole ring opens up and the oxime group is drawn into the overall chromophore system. It is known that halochromic shifts for similar dyes do not exceed 30 nm [8]. Institute of Organic Chemistry, Ukrainian Academy of Sciences, Kiev. Dnepropetrovsk Engineering and Construction Institute, Dnepropetrovsk. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 183-189, February, 1992. Original article submitted March 12, 1990. 148 0009-3122/92/2802-0148812.50 9 1992 Plenum Publishing Corporation