Intramolecular diels-alder reactions. XI. Modal selectivity in the syntheses of some parent cyclolignan lactones

Ph(C₂)CH₂Cl and Ph(C₂)'CO₂Na [where (C₂) = -C=C- or trans-CH=CH-, (C₂)' = -C=C- or cis-CH=CH-] reacted in refluxing dimethylformamide to yield unsaturated esters Ph(C₂)'CO₂-CH₂(C₂)Ph and/or their intramolecular Diels-Alder cyclization products (cyclolignan lactones). It was found that modal selectivity for cyclization in DMF sometimes varies from that found previously with acetic anhydride as solvent. Two new parent tetrahydrocyclolignan lactones were synthesized.     

Condensed thiophenes from sulfur bridging. II. Catalyzed reaction of azabiaryls with hydrogen sulfide

Sulfur bridging inlo the phenylpyridines, 2- and 3-phenylquinolines, and the symmetric bi-pyridines was effected by means of hydrogen sulfide and an alumina catalyst at 630° to give [1]benzothienopyridines, [1]benzothienoquinolines, and thienodipyridines, respectively. Structures of products were assigned on the bases of spectral and chromatographic studies, as well as of separate syntheses. Relative yields of the various products are rationalized in terms of a model for interaction between a chemisorbed sulfur atom and the substrate molecule.     

Chemistry of thienopyridines. XXXV. Synthesis,tautomerism, and reactions of quinoline and thienopyridine systems which bear a 1-carboethoxy-1-cyanomethyl substituent in the pyridine ring,part 2

A comparison is made amongst the isosteric Systems quinoline, thieno[2,3,-b]pyridine, and thieno[3,2-b]-pyridine which bear the 1-carboethoxy-1-cyanomethyl substituent (R) alpha or gamma to the heterocyclic nitrogen atom. Treatment of thieno[3,2-b]pyridine 4-oxide with ethyl cyanoacetate and acetic anhydride at room temperature (Hamana reaction) gives the alpha R-derivative 6 (27%), formulated as an intramolecular H-bonded structure. Neither 6 nor its quinoline alpha analog reacts with refluxing acetic anhydride, while the quinoline gamma isomer 8 , existing as NH and CH tautomers, yields an N-acetyl derivative 10 (70%) under similar conditions. For each of 6 and 8 one can isolate two crystalline forms which differ considerably in color. Compound 10 and its gamma analog in the thieno[2,3-6]pyridine series (previously obtained directly from a Hamana reaction) serve as acetylating agents for aniline, 1-aminobutane, morpholine, and cholesterol. Correlations and contrasts in the three Systems are presented.     

The insertion and extrusion of heterosulfur bridges. IX: Sulfur bridging in 2-phenylnaphthalene

Sulfur bridging of 2-phenylnaphlhalene ( 3 ) to form benzo[b ]naphtho[2,1-d]thiophene ( 5 ) (main product) and the isomeric benzo[b]naphtho[2,3-d]thiophene ( 4 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450–630° in a flow system (maximum yield 33% at 500°). The low yield is ascribed to decompositions of both 4 and 5 under reaction conditions.     

Broadband Noise in Orthorhombic TaS3

We report experimental results on the broadband noise in sliding charge density wave conductor orthorhombic TaSn. The experimental results are in excellent agreement with a phenomenological model based on fluctuations in threshold field due to deformations of the sliding condensate.     

Chemistry of thienopyridines. XXXIII. Synthetic routes to 5- and 7-substituted thieno[3,2-b]pyridines from the N-oxide

Thieno[3,2-b]pyridine ( 1 ) is oxidized to N-oxide 1a by means of m-chloroperoxybenzoic acid (83%). Compound 1a forms adducts with hydrogen chloride and picric acid and gives ring substitution alpha or gamma to the heteronitrogen atom. Thus, 1a plus nitric and sulfuric acids produces the 7-nitro-N-oxide 1m (63%), or plus phosphorus oxychloride gives a mixture of 5-chloro and 7-chloro ( 1j ) derivatives of 1 . Compound 1m is convertible into a variety of other derivatives of 1 , viz. 7-chloro-N-oxide, 1j , 7-bromo-N-oxide, 7-nitro and 7-amino. 5-Cyano- 1 , formed from 1a , is, in turn, transformed into a methyl imidate (93%), cyclic amidines, and a 5-tetrazolyl- 1 (91%). These results confirm the prediction that 1a , thieno[2,3-b]pyridine-4-oxide and quinoline 1-oxide should exhibit closely similar (i.e. analogous) chemical reactions.     

n-Butyl by-products in the syntheses of 2-(1- and 2-naphthyl)pyridines via lithiation

By-products in the syntheses of 2-(1- and 2-naphthyl)pyridines by successive treatments of 1- and 2-bromonaphthalenes with (a) n-butyllithium in ether and (b) pyridine are identified as 5-butyl-2-(1-naphthyl)pyridine and, tentatively, 5-butyl-2-(2-naphthyl)pyridine, respectively. It is proposed that these by-products result from reaction of intermediate compounds 1-lithio-2-naphthyl-1,2-dihydropyridines and 1-bromobutane.     

Two syntheses of 5-chloro-3-(2-thienyl)-2,1-benzisoxazole

5-Chloro-3-(2-thienyl)-2,1-benzisoxazole ( 2 ) resulted from condensation of (a) o-nitrobenzaldehyde with thiophene in the presence of hydrochloric acid and (b) p-chloronitrobenzene with 2-cyanomethylthiophene. Spectral data for ( 2 ) are presented and interpreted.