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Titolo:
PREPARATION OF CONGESTED THIOPHENES CARRYING BULKY SUBSTITUENTS ON THE 3-POSITIONS AND 4-POSITIONS AND THEIR CONVERSION TO THE BENZENE-DERIVATIVES
Autore:
NAKAYAMA J; HASEMI R; YOSHIMURA K; SUGIHARA Y; YAMAOKA S; NAKAMURA N;
Indirizzi:
SAITAMA UNIV,FAC SCI,DEPT CHEM URAWA SAITAMA 338 JAPAN HOSEI UNIV,FAC ENGN,DEPT CHEM MAT KOGANEI TOKYO 184 JAPAN
Titolo Testata:
Journal of organic chemistry
fascicolo: 15, volume: 63, anno: 1998,
pagine: 4912 - 4924
SICI:
0022-3263(1998)63:15<4912:POCTCB>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR-MAGNETIC-RESONANCE; LOW-VALENT TITANIUM; GENERAL-SYNTHESIS; DIKETO SULFIDES; 3,6-DISUBSTITUTED PYRIDAZINES; CONVENIENT SYNTHESIS; ADJACENT POSITIONS; 1ST SYNTHESIS; 3,4-DI-TERT-BUTYLTHIOPHENE; SULFURATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
65
Recensione:
Indirizzi per estratti:
Citazione:
J. Nakayama et al., "PREPARATION OF CONGESTED THIOPHENES CARRYING BULKY SUBSTITUENTS ON THE 3-POSITIONS AND 4-POSITIONS AND THEIR CONVERSION TO THE BENZENE-DERIVATIVES", Journal of organic chemistry, 63(15), 1998, pp. 4912-4924

Abstract

Highly congested thiophenes, 3,4-di-tert-butyl-, 3,4-di(1-adamantyl)-, 3,4-dineopentyl-, and 3-(1-adamantyl)-4-tert-butylthiophenes (4a-d),were prepared in satisfactory overall yields by intramolecular reductive coupling of 3-thiapentane-1,5-diones (1a-d) followed by acid-catalyzed dehydration of the resulting thiolane-3,4-diols (2a-d). Experimental procedures of this; thiophene synthesis are fully described. Oxidation of the thiophenes 4a-d with m-CPBA gave the corresponding thiophene 1,1-dioxides 13a-d in good yields. The Diels-Alder reactions of 13a-d with phenyl vinyl sulfone gave o-di-tert-butyl-, o-di(1-adamantyl)-, o-dineopentyl-, and o-(1-adamantyl)-tert-butylbenzenes (17a-d) directly in high yields with loss of benzenesulfinic acid and sulfur dioxide. The dioxides 13a-d also underwent Diels-Alder reactions with alkynic dienophiles to give the corresponding benzene derivatives carrying two bulky substituents on adjacent positions. Pyridazines 25b,c, carrying bulky substituents on the 4- and 5-positions, were also synthesizedthrough Diels-Alder reaction of 13b,c with PTAD. Dimethylation of the2- and 5-positions of 13a-d was attained by treatment with strong bases followed by reactions with methyl iodide. The resulting tetrasubstituted thiophene 1,1-dioxides 14a-d reacted with DMAD to give highly congested hexasubstituted benzene derivatives 15a-d in good yields. Finally, structural features of the congested molecules are discussed on the basis of NMR analyses. Typically, the barriers to rotation (Delta Hdouble dagger) about the benzene to the bulky substituents of 15a,c,dwere determined to be 8.59, 15.3, and 7.40 kcal/mol, respectively, byNMR total line-shape analysis.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/04/20 alle ore 10:09:34