Synthesis of spirocyclic β-methylene-γ-lactone utilizing hydroxymethylation of functionalized allylsilane
摘要:
A new spiro-beta-methylene-gamma-lactone annulation reaction is addressed for the synthesis of 4-methylene-2-oxaspiro[4.5]decan-1-one and its derivatives. 2-Cyclohexylidene-3-trimethylsilylprop-1-yl pivalate, obtained from cyclohexanone, was hydroxymethylated followed by desilylation to afford 2-[(1-hydroxymethyl)cyclohexyl]prop-2-en-1-yl pivalate and its -1-en-1-yl isomer. The former was oxidized to carboxylic acid followed by lactonization to the above compound. It was found that the stereochemistry of the hydroxymethylation reaction depends on the substituent on the cyclohexane ring. (C) 2002 Elsevier Science Ltd. All rights reserved.
The 5-exo-dig radical cyclisation reaction of the bromoacetals 9, obtained from the enol ethers 8, and treatment of the resulting hemiacetal 10 with JonesⲠreagent transforms the cyclic ketones 7 and 12 into α-spiro-β-methylene-γ-butyrolactones 11 and norbakkenolide-A 2.