1-Bromo-2-ethoxycyclopropyllithium: A Synthetic Equivalent of 2-Lithio-or 3-Lithiopropenal. Application to the Synthesis of Juvenile Hormone (JH-II), β-Sinensal, and Jasmonoids
resulting lithium carbenoid 3 was allowed to react with various electrophiles to give 1-substituted trans-1-bromo-2-ethoxycyclopropanes (1) in good yields. The trans relationship of Br and OEt groups was found particularly pertinent to the ethanolysis of 1 producing 2-substituted propenal diethyl acetal derivatives. The reaction has been applied to 1-methoxycyclohexene–dibromocarbene adducts, giving