Arsenic Compounds in Organic Synthesis: Pentamethinium Salts from Aminoarsanes and Pyrylium Salts

✍ Scribed by Dr. Yves Madaule; Myriam Ramarohetra; Dr. Jean-Gérard Wolf; Prof. Dr. Jean-Paul Declercq; Dr. Antoine Dubourg

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 379 KB
• Volume: 30
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.199109941

✦ Synopsis

Most promising for future exploration are the cocyclizations of the enantiomerically pure nucleoside models 4b-d, bearing what might be considered chiral auxiliary sugar substituents. Their potential utility is demonstrated in the highly diastereoselective construction of 6e.

5. As discussed previously,[3, 61 the position of the cobalt atom relative to those of the adjacent cyclohexadiene tertiary hydrogens is readily ascertained exploiting the metal's distinctive magnetic anisotropy. In this way, the major diastereomer of 6d and 6e was assigned the syn-configuration. To corroborate these conclusions and perhaps obtain some clues with respect to the selectivity of the addition of 4c to 5t1, an X-ray structural analysis of 6e (major isomer) was performed (Fig. l).['] Fig. 1. Structure of 6 e (major isomer) in the crystal (SHELXTL). Selected distances [A] and angles ["I: Co-C6 2.014(3), CO-C7 1.960(3), Co-C12 1.991(3),