Four- and eight-carbon homologation of benzaldehyde by (1Z,3Z)- butyltelluro-1,3-butadiene: Synthesis of navenone B: Alarm pheromone of the mollusk navanax inermis

摘要

Four- and eight-carbon homologation of benzaldehydes is described. The hydrotel-luration of (Z)-1-methoxy-but-1-en-3-ynes 1 afforded (1Z,3Z)-1-butyltelluro-4-methoxy-1,3-butadiene 2, this compound 2 underwent a Te=Li exchange reaction, and the butadienyl-lithium 3 obtained reacted with benzaldehyde to form the corresponding allylic alcohol 4 with total retention of configuration. The allylic alcohol 4a formed underwent acidic hydrolysis, resulting in 5-phenyl-(2E,4E)-dienal 5 (four-carbon homologation of benzaldehyde). Product 5 reacted with the butadienyllithium 3, affording the alcohol 9-phenyl-(1-Z,3Z,6E,8E)-1-methoxy-5-hydroxy-nonatetraene 6, which was hydrolyzed or spontaneously transformed into 9-phenyl-(2E,4E,6E,8E)-tetraenal 7, completing the eight-carbon homologation of benzaldehyde. Reaction of 9-phenyl-nona-(2E,4E,6E,8E)-tetraenal 7 with methyllithium in tetrahydrofuran afforded (3E,5E,7E, 9E)-10-phenyl-deca-3,5,7,9-tetraen-2-ol 8. The product of the reaction described was employed in the synthesis of (3E,5E,7E,9E)-10-phenyl- deca-3,5,7,9-tetraen-2-one 9, which is known as navenone B, an alarm pheromone of the mollusk Navanax inermis.