Károly Lempert

Simple and condensed β-lactams. Part 22. An unprecedented ring transformation accompanying dephthaloylation of a 3-phthalimidoazetidin-2-one☆

Abstract Dephthaloylation of 3-phthalimidoazetidin-2-one 1a with methylhydrazine affords the ring transformation product 2b, rather than the expected 3-aminoazetidin-2-one 1b. Independently prepared azetidinone 1b, when treated with sodium hydroxide or methylhydrazine, is isomerized to compound 2b. A mechanism is suggested for transformation 1a → 2b . - The tautomeric structures of the majority of the potentially tautomeric compounds described were established.

On the anomalous behaviour of (3RS,4RS)-[(2RS)-3-acetylthiazolidin-2-yl]-1-(4-methoxyphenyl)azetidin-2-ones towards cerium(IV) ammonium nitrate (CAN). An unprecedented oxidative ring transformation.

Abstract Starting with (2RS,3RS)-1-(4-methoxyphenyl)-4-oxo-3-phthalimidoazetidine-2-carbaldehyde (1) the two diastereoisomeric 4-(3-acetylthiazolidin-2-yl)-1-(4-methoxyphenyl)-3-phthalimidoazetidin-2-ones 4a and 5a were prepared and converted into their 3-allyloxycarbonylamino analogues 4c and 5c, respectively. While the (3RS,4RS,2′SR) isomers 4a and 4c were readily N-deprotected with cerium (IV) ammonium nitrate (CAN) to yield the expected 6a and 6c, respectively, treatment of the (3RS,4RS,2′RS) isomers 5a and 5c with CAN led to compounds 7a and 7c, respectively, via oxidative ring transformation. The structure of compound 7a was established by an X-ray diffraction study. A rationale, based on AM1 and MMX calculations is given for the dissimilar behaviour of the diastereoisomers.

Electron deficient heteroaromatic ammonioamidates. Part 26. N-(quinazolin-3-io)amidates. Part 13. Phototransformations of an N-(quinazolin-3-io)thioamidate and of a 10bH-1,3,4-thiadiazolo[3,2-c]quinazoline, the ring isomer of an N-(quinazolin-3-io)thioamidate, and the photochemical formation of some 4,4′-biquinazolinyls

Irradiation of the N-(quinazolin-3-io)thioamidate (10a) in ethanol and butylamine solution furnished, in addition to several other compounds, the 4,4′-biquinazolinyl (12a), the quinazolinyl alcohol (13a) and the quinazolinyl ketone (13b), respectively, the mesoionic triazoloquinazolinylium thiolate (18a)and the corresponding olate (18b) as novel type photolysis products. In contrast irradiation of the 10bH-1,3,4-thiadiazolo[3,2-c]quinazoline (11b), the ring isomer of the N-(quinazolin-3-io)thiomidate (10b) furnishes, with cleavage of either the quinazoline or the thiadiazole ring, a mixture of the thiadiazoles (21a,b), and the quinazoline derivatives (14a), (22a,b)in addition to 3,4-dimethoxybenzonitrile.Irradiation of various sulphur-containing quinazoline derivatives, including the quinazolinethiones (14a,e), the methylthioquinazoline (13f) and the diquinazolinyl disulphide (24a), leads to the formation of 4,4′-biquinazolinyls (12a) and (12b), respectively. Irradiation of the quinazoline (13c), which carries no sulphur-containing substituent, does not lead to the formation of the biquinazolinyl (12a); irradiation of a mixture of quinazoline (13e) and quinazolinethione (14a) gives rise to the formation of a mixture of biquinazolinyls (12a–c) with incorporation of the ring of the sulphur-free starting quinazoline (13e) into the products (12a) and (12b).

ELECTRON DEFICIENT HETEROAROMATIC AMMONIOAMIDATES. XVI. THE SYNTHESIS AND PHOTOCHEMISTRY OF ETHYL N-(2-METHYL-4-METHYLENE-6,7-METHYLENEDIOXY-3,4-DIHYDRO-3-QUINAZOLINYL)-N-PHENYLCARBAMATE

Abstract Irradiation through Pyrex of the N-(dihydroquinazolinyl)carbamate 3c in ethanol furnishes mixtures (Scheme 1) of two photoisomers (2c and 4a), two dimeric products: the 1,2-bis(4-quinazolinyl)ethane 5 and the (p-phenylene)dicarbamate 6, and of ethyl N-phenylcarbamate. The latter, as well as compounds 4a and 5 are formed also on irradiation of compound 2c. The radicals 9 and 10, formed by homolysis of the N-N bond of 3c as well as of the CH2-N bond of 2c are considered to be the primary photoproducts of both reactions, and to lead, by various recombination processes, to compounds 2c, 4a, 5 and 6, and to ethyl N-phenylcarbamate by hydrogen abstraction. It is not clear at present whether concerted photochemical [1,3] shifts contribute to the formation of 2c and 4a.

Simple and condensed β-lactams, part 31. Acid catalyzed ring closures and ring transformations of some 3-aryloxy-4-oxoazetidine-2-carbaldehydes

Abstract Carbaldehydes 1a and 1b, when treated with Lewis or Bronsted acids in non-aromatic solvents or in nitrobenzene afford dihydrochromeno[3,2-b]azet-2(1H)-ones of types 4–6 and 10. In toluene, chloro- and fluoro-benzene related compounds of types 7–9 were obtained, in the last named two solvents accompanied by pyrrolidin-2-one derivatives 11–15.

Simple and condensed β-lactams. Part 29. Synthesis and base-catalyzed ring transformation of 4-[(2RS,3SR)-3-hydroxy-1-(4-methoxyphenyl)-4-oxoazetidin-2-yl)]thiazol-2(3H)-one☆

4-[(2RS,3RS)-3-Hydroxy- (1b) and -3-(4-chlorophenoxy)-1-(4-methoxyphenyl)-4-oxoazetidin-2-yl]thiazol-2(3H)-one (16b) were synthesised. While the former was smoothly rearranged into (5RS)-5-hydroxy-7-(4-methoxyphenyl)-1,5-dihydrothiazolo[3,4-a]pyrazine-3,6(7H)-dione (7b) on treatment with Na2CO3 under mild conditions, the latter was found to be stable to Na2CO3 under the same conditions. The structural prerequisites for type 1 → 7 ring transformations, including cleavage of the 3–4 bond (azetidin-2-one numbering) of the β-lactam ring are defined.

Simple and condensed β-lactams. Part 27. Reaction of 1-(4-methoxyphenyl)-4-(tetrazol-5-yl)azetidin-2-one and 1-(4-methoxyphenyl)-5-(tetrazol-5-yl-methyl)pyrrolidin-2-one with cerium(IV) ammonium nitrate (CAN)☆

Abstract Treatment of pyrrolidinone 3a with CAN under the usual conditions leads to formation of spiro compound 12, rather than to N-demethoxyphenylation. A study of the reactions of compound 12 with sodium chloride and sodium iodide furnished the proof for our assumption that the related non-isolable compounds 6 and 11 are the intermediates of the anomalous reactions of compounds 1a and 2a, respectively, with CAN.

The reduction of triarylcarbenium ions by alcohols: simple hydride transfer or concerted breakdown of ortho-adducts ?

Reduction of tris-(4-methoxyphenyl)methyl chloride (2) by refluxing methanol to tris-(4-methoxyphenyl)methane (3) is, as shown by 2H labelling, accompanied by exchange of methoxy-groups between solvent and substrate. This exchange reaction appears to be the first recognized example of an SN2-Ar reaction of a triarylcarbenium ion and involves the intermediacy of the para-adduct (9a) which implies that in the course of the reduction of triarylcarbenium ions by n-nucleophiles, formation of the related type (1)ortho-adducts is possible as required by the Olah–Svoboda mechanism.

Electron deficient heteroaromatic ammonioamidates. Part 25. N-(Quinazolin-3-io)amidates. Part 12. The synthesis of n-(6,7-dimethoxy-2-methylquinazolin-3-io)ethoxythioformamidate and of 2-(3,4-dimethoxyphenyl)-8,9-dimethoxy-5-methyl-10bH-[1,3,4]-thiadiazolo [3,2-c] quinazoline, the ring isomer of N-(6,7-dimethoxy-2-methylquinazolin-3-io)-3,4-dimethoxy(thiobenzamidate)

The synthesis of N-(6,7-dimethoxy-2-methylquinazolin-3-io)ethoxythioformamidate (7a) has been carried out starting with the thioacylhydrazone (5a)via cyclization of the acetylamino thioacylhydrazone (6a). An analogous attempt to synthesize the related thiobenzamidate (7b) failed and furnished instead the cyclic form of the desired product, the [1,3,4] thiadiazolo [3,2-c] quinazoline (12b). In contrast to the thioacylhydrazones (5a) and (6a) the related thiobenzoylhydrazones (5b) and (6b) are shown to exist as their cyclic isomers, the thiadiazolines (8b) and (9b) respectively, under the conditions studied. Cyclization of (9b) furnished the thiadiazoloquinazoline (12b). The existence of this cyclic form (12b), and the absence of the dimer (17) of the quinazolinio(thioamidate)(7b) are in sharp contrast to the case of the related quinazolinioamidates (1).

Über die Orientierung bei der Kondensation von Benzil mit monosubstituierten Guanidinen

Condensation of benzil with two monosubstituted guanidines in the presence of 50 mol% of potassium hydroxide leads to the formation of 2-(subst. imino)-4, 4-diphenyl-imidazolidin-5-ones (Ia, b); by reduction of the potassium hydroxide used the formation of these products is more or less driven back in favour of the formation of 3-substituted 5, 5-diphenyl-glycocyamidines (Ic, d). A possible explanation for these orientation phenomena is given.