首页|Benzannulated cyclooctanol derivatives by samarium diiodide induced intramolecular carbonyl-alkene coupling - Scope, limitations, stereoselectivity

Benzannulated cyclooctanol derivatives by samarium diiodide induced intramolecular carbonyl-alkene coupling - Scope, limitations, stereoselectivity

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A series of gamma-oxo esters 27-34 was prepared from methyl 2-silyloxycyclopropanecarboxylates 1-9 as key building blocks in a flexible modular synthesis, Their samarium diiodide promoted cyclization to benzannulated cyclooctanol derivatives was systematically investigated. Samariurn ketyl compounds derived from aldehydes 27 and 28 mainly provided tricyclic gamma-lactones 38 and 39 as a result of a cis-selective ring-closure process, whilst the related ketones 29-31 underwent transselective reductive cyclization to furnish the expected benzannulated cyclooctanol derivatives 43-45 in moderate to excellent yields. With cyclohexanones 33 and 34 an interesting stereochemical matched/mismatched situation was observed. Whereas diastereomers 33a and 34a smoothly afforded tricyclic products 47 and 48 in good yields, compound 33b with apparently mismatched configuration did not undergo the samarium. diiodide promoted ring-closure process. An explanation for this intriguing behaviour is presented, together with an explanation for the cis/trans selectivity. Tricyclic gamma-lactone 38 could be smoothly deprotonated at one bridgehead and the generated lithium enolate was trapped with suitable alkyl halides. Remarkably, a clean alpha-hydroxylation of 38 and 39 by direct employment of molecular oxygen was possible, providing high yields of the corresponding tertiary alcohols 54 and 55. These results demonstrate that the cyclization products prepared can easily be converted into higher functionalized berizannulated cyclooctane derivatives.

samarium diiodidestyrene derivativesketoneselectron transfercyclooctanesmedium-sized ringsACCEPTOR-SUBSTITUTED CYCLOPROPANESKETYL-OLEFIN CYCLIZATIONRING-CLOSING METATHESISMEDIUM-SIZED RINGSORGANIC-SYNTHESISSCHIZANDRA-ARISANENSISSEQUENCED REACTIONSCRYSTAL-STRUCTUREIODIDEEFFICIENT

Reissig HU、Khan FA、Czerwonka R、Dinesh CU、Shaikh AL、Zimmer R

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Free Univ Berlin, Inst Chem & Biochem, D-14195 Berlin, Germany

Tech Univ Dresden, Inst Organ Chem, D-01069 Dresden, Germany

2006

European journal of organic chemistry

European journal of organic chemistry

CCR
ISSN：1434-193X
年,卷(期)：2006.(19)