Synthesis of (1 R,4 E,5 S)-4-{[( E)-(azinyl)diazenyl]methylidene}-1,8,8-trimethyl-2-oxabicyclo[3.2.1]octan-3-ones and (1 R,4 R,5 R)-4-([1,2,4]triazolo[4,3- x]azin-3-yl)-1,8,8-trimethyl-2-oxabicyclo[3.2.1]octan-3-ones

• Published in: Tetrahedron: asymmetry Vol. 16; no. 17; pp. 2927 - 2945
• Main Authors: Grošelj, Uroš, Bevk, David, Jakše, Renata, Meden, Anton, Stanovnik, Branko, Svete, Jurij
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.09.2005
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/j.tetasy.2005.07.032

4-[(Heteroaryldiazenyl)methylidene] and 4-([1,2,4]triazolo[4,3- x]azin-3-yl) substituted (1 R,5 R)-4-1,8,8-trimethyl-2-oxabicyclo[3.2.1]octan-3-ones 6/ 6′ and 7/ 7′ were obtained in a one-pot transformation of the enamino lactone 2 with hydrazinoazines 3a– g followed by oxidation of the intermediate mixture of isomeric enehydrazines 4/ 4′ and hydrazones 5/ 5′ with lead tetraacetate. The oxidation selectivity was dependent on the ratio of isomeric intermediates 4/ 4′ and 5/ 5′. Treatment of 7b with lead tetraacetate led to α-acetoxylated compound 11, while bromination of 9b afforded a 1:1 mixture of α-bromination products 12 and 12′, which were separated by medium pressure liquid chromatography (MPLC). The structures of intermediates and products were confirmed by NMR and X-ray diffraction.