Síntese de novas fitotoxinas derivadas do 8-oxabiciclo[3.2.1]oct-6-en-3-ona Synthesis of new phytotoxins derived from 8-oxabicyclo[3.2.1]oct-6-en-3-one

• Main Authors: Luiz C. A. Barbosa, Célia R. A. Maltha, Antônio J. Demuner, Flávia R. Ganen, Antônio A. da Silva
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Química 2005-06-01
• Series: Química Nova
• Subjects: [4+3] cycloaddition; oxyallyl cations; herbicides
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422005000300015

<abstract language="eng">The [4+3] cycloaddition was utilized in order to prepare 8-oxabicyclo[3.2.1]oct-6-en-3-one (1) derivatives. The correspondent acetonide 6 was converted into several alcohols (11-16). Addition of aryllithium reagents to 6 resulted in 3-(2-fluorophenyl)-6,7-exo-isopropylidenedioxy -8-oxabicyclo[3.2.1]octan-3alpha-ol (11, 72%) and 3-(2,4-dimethoxyphenyl)-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan -3alpha-ol (16, 20%). The 3-butyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 alpha-ol (15, 56%) was obtained through a Grignard reaction. Reduction of 6 resulted in 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 beta-ol (7, 62%) and 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 alpha-ol (8, 20%). The alcohols were treated with thionyl chloride in pyridine, and the corresponding alkenes were obtained with 31-80% yield. The effect of these compounds on the development of radicle and aerial parts of Sorghum bicolor was evaluated.