Schmidt rearrangement of 1,2,3,5,10,10a-hexahydropyrrolo[1,2-b]-isoquinoline-3,10-diones

The Schmidt rearrangement of 1,2,3,5,10,10a-hexahydropyrrolo[1,2-b]isoquinoline-3,10-diones has been studied. The structure of the lactams obtained has been determined by chemical reactivity and characterized by means of ir, ¹H and ¹³C nmr spectroscopy.     

Synthesis of pyrrolo[1,2-b]cinnolines

The synthesis of the pyrrolo[1,2-b]cinnoline analogs 2 and 4–13 is described. The key step of this synthesis involves an intramolecular aromatic halide displacement on [2-(2-halobenzoyl)pyrrol-1-yl]carbamic acid esters. Several reactions of these cinnoline analogs with electrophilic reagents have been investigated.     

Methods for the synthesis of pyrrolo[1,2-b]pyridazine and pyrrolo[1,2-b]cinnoline derivatives (microreview)

Chemistry of Heterocyclic Compounds - This microreview considers methods for the synthesis of pyrrolo[1,2-b]pyridazine derivatives as well as their benzo-fused analogs –...     

The preparation of the benzo[4,5]cyclohepta[1,2-b]pyrazine and benzo[4,5]cyclohepta[1,2-b]quinoxaline systems

Benzo[4,5]cyclohepta[1,2-b]quinoxaIine 2 , benzo[4,5]cyclohepta[1,2-b]pyrazine 3a and benzo[4,5]cyclohepta[1,2-b]quinoxaline 4 were prepared from 4,5-benzotropolone and 1,2-phenylenediamine, ethylenediamine and 1,2-diaminocyclohexane, respectively. Compound 3a was methylated to 3b .     

Synthesis of pyrrolo[2,3-b]azepine-4,7-dione derivatives

The Dieckmann reaction has been successfully applied for the first time in the synthesis of pvrrolo[2,3-b)]azepines.     

Investigations of substituted benzofuran-3-carboxylates,benzo[1,2-b:4,5-b']difurans and benzo[1,2-b:4,3-b']difurans

The Michael addition of ethyl acetoacetate to benzoquinone, toluquinone, and chlorobenzo-quinone leads to formation of substituted 5-hydroxybenzofuran-3-earboxylates and linear benzo-[1,2-b:4,5-b']difurans. The previously reported structural proof for the benzodifurans obtained from chlorobenzoquinone and toluquinone, although correct in the conclusion, is shown to be invalid. Proof of the linear benzodifuran structures was obtained by comparison of the uv spectra with authentic angular benzo[1,2-b:4,3-b']difurans.     

Synthesis, properties, and structures of benzo[1,2-b:4,5-b']bis[b]benzothiophene and benzo[1,2-b:4,5-b']bis[b]benzoselenophene

Employing two consecutive cyclization reactions, benzo[1,2-b:4,5-b']bis[b]benzochalcogenophenes, which are pi-extended heteroarenes, were efficiently synthesized. Their electronic and crystal structures were elucidated on the basis of UV-vis spectra, electrochemical measurements, and X-ray structural analyses.     

Unusual formation of a novel pyrrolo[1′,2′:1,2]pyrido[3,4-b]indole

Reaction of 1-methyl-3,4-dihydro-β-carboline 1 with methyl glycidate 4 gave the novel tetracyclic conjugated γ-lactam, 2-methylpyrrolo[1′,2′:1,2]pyrido[3,4–6]indol-3-one 5 . The same compound 5 was obtained in higher yield when 1 was treated with methyl 2-methoxyacrylate 7 . Sodium borohydride treatment of 5 resulted in the cleavage of lactam to yield the unexpected alcohols 8 and 9 .     

Synthesis and X-ray structure of a new pyrrolo[1,2-b]-pyridazine derivative

The synthesis, characterization and X-ray crystal structure of 2-(4-chloro-phenyl)-7-methylpyrrolo[1,2-b]pyridazine are reported. The compound crystallizes in the space group P2(1)/c (No.14) with a =3.8568(1), b = 11.0690(3), c = 26.4243(7) A, beta =92.777(1) degrees and Z = 4. Accurate molecular parameters for the novel heterocyclic system were obtained from intensity data collected at 113K. The molecule assumes a planar conformation in the crystal and the packing is based on pi-pi stacking with interplanar spacing 3.400 ?, typical of aromatic molecules with potential for displaying useful optical properties.     

Studies of pyridazine compounds. XXVI. The synthesis of Pyridazino[4,5-b]pyrrolo[1,2-d][1,4]oxazines and a pyridazino[4,5-b]pyrrolo[1,2-d][1,4]thiazine

The tricyclic oxazines 3 and 5 were obtained by ring closure of (2-hydroxymethyl-1-pyrrolidinyl)-3(2H)-pyridazinones 2d,e,g , respectively, prepared from 4,5-dichloro-3(2H)-pyridazinones with L-prolinol. The synthesis of the thiazine analogue 4a was achieved by treatment of 2d with thionyl chloride and the subsequent reaction with sodium sulfide. The structures of the compounds were supported by spectroscopic evidence.     

Thermolyzed products of naphth[1,2-d]imidazo[2,1-b]-thiazole-2,3-dione

Themolysis of naphth[1,2-d]imidazo[2,1-b]thiazole-2,3-dione ( 1 ) in dimethylformamide gave an intermediate 2-isocyanatonaphtho[1,2-d]thiazole ( 2 ), which underwent [4 + 4] cyclodimerization to yield dinaphtho-[1″,2″:4,5;1′″,2′″:4′,5′]dithiazolo[3,2-a:3′,2′-e]-1,3,5,7-tetrazocine-9,19-dione ( 3 ). The possible [4 + 2] cycloadduct, 3-(2-naphtho-[1,2-d]-thiazolyl)naphtho[1′,2′:4,5]thiazolo[3,2-a]-1,3,5-triazine-2,4-dione ( 4 ), an usual dimer type of heterocyclic isocyanates was not produced. Discrimination between the two isomers was established on the basis of spectral analyses.     

Synthesis of novel benzo[h] [1,6]naphthyridines via a rearrangement of hexahydro‐5H‐pyrrolo [2,1 ‐c] [1,4]benzodiazepines

Heating of hexahydro‐5H‐pyrrolo[2,1‐c][1,4]benzodiazepine‐2,5,11‐trione in boiling phosphoryl chloride led to a rearranged product like 3,5‐dichlorobenzo[h][1,6]naphthyridine. This structure was established from X‐ray diffraction analysis.     

Derivatives of benzo[5,6]cyclohepta[1,2-b]thiophene. Synthesis of 2,3,7,8-tetrahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline and 1,2,3,7,8,11b-hexahydro-3-oxothieno[1,2-b]cyclohepta[5,6,7-de]isoquinoline

The synthesis of the title compounds was carried out by cyclization via isocyanate of (E)-4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylideneacetic acid and 4,5-dihydro-10H-benzo[5,6]cyclohepta[1,2-b]-thiophene-10-ylacetic acid respectively, which were obtained by the Wadsworth-Emmons modification of the Wittig reaction of 4,5-dihydro-10H-10-oxobenzo[5,6]cyclohepta[1,2-b]thiophene and triethyl phosphonacetate. The structures of these new compounds are described.     

The transformation of saccharin into derivatives of lmidazo[1,2-b] [1,2]-benzisothiazole and benzo[g] [1,2,5]thiadiazocine

Reaction of 3-(2-hydroxyethylamino) benzo[d]isothiazole 1,1-dioxide ( 5a ) with thionyl chloride gives a mixture of the expected chloroethyl derivative ( 5h ) and the rearranged saccharin 2-(2-aminoethyl)-3-oxo-2,3-dihydrobenzo[d]isothiazole 1,1-dioxide hydrochloride ( 6a ). Separate treatment of the chloroethyl compound ( 5h ) with dilute alkali gives the expected cyclization product 2,3-dihydroimidazo[1,2-b] [1,2] benzisothiazole 5, 5-dioxide ( 7a ). Acidification of the liquors of the above reaction yields the ring expanded derivative 6-oxo-3,4,5,6-tetrahydro-[2H]benzo[g][1,2,5]thiadiazocine 1,1-dioxide ( 12f ), a representative of a new ring-system. Treatment of the imidazo derivative ( 7a ) with concentrated hydrochloric acid again yields the N-substituted saccharin ( 6a ) which upon treatment with alkali also produces the thiadiazocine ( 12f ). In contrast, treatment of the imidazo compound ( 7a ) with alkali leads to attack on the sulphonamide function to give 2-(2-imidazolin-2-yl)benzenesulphonic acid ( 8 ). It is suggested that the multitude of chemical interconversions which can be induced within this series of compounds (Scheme II) can only be accounted for if two separate cyclol intermediates are invoked. Related reactions observed with variously substituted derivatives of the starting saccharin derivative ( 5a ) are discussed as are the spectral properties and chemical reactivity of the new compounds prepared.