Synthesis with Organoboranes; 4. Transformation of Olefins into Homoallylic Alcohols, β,γ- and α,β-Unsaturated Ketones via Allylic Diethylboranes
Allylic diethylboranes are obtained from 1-methylcycloalkenes and 2-alkenes, respectively, via metalation with trimethylsilylmethylpotassium (generated in situ from bis(trimethylsilylmethyl)mercury and potassium sand) and subsequent reaction with chlorodiethylborane.The allylic boranes react diastereoselectively with aldehydes to give homoallylic alcohols.The alcohols are oxidized with pyridinium dichromate to β,γ-unsaturated ketones, which in turn are isomerized with aluminum oxide to conjugated ketones.The transformation provides access to 2-methylene-1-acylcycloalkanes, 3-acyl-1-alkenes and 3-acyl-2-alkenes not readily available by Friedel-Crafts acylation of olefins.
SYNTHESIS OF 2-SUBSTITUTED METHYLENECYCLOALKANES FROM 1-(DIALKYLBORYLMETHYL)CYCLOALKENES
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Bubnov, Yu. N.,Lavrinovich, L. I.
p. 339 - 343
(2007/10/02)
Regiospecific Synthesis of β, γ-Unsaturated Ketones from Allylic Alcohols. Claisen Rearrangement of α-Allyloxy Ketone Enol Derivatives
β,γ-Unsaturated ketones are prepared with regiospecific C-C bond formation at the former γ-position of primary, secondary, or tertiary allylic alcohol precursors by a process involving sigmatropic Claisen rearrangement of intermediate α-allyloxy ket
Kachinsky, Joseph L. C.,Salomon, Robert G.
p. 1393 - 1401
(2007/10/02)
A NEW GENERAL APPROACH TO 2-SUBSTITUTED METHYLENECYCLANES USING 1-(DIALKYLBORYLMETHYL)CYCLOALKENES
A novel method for the synthesis of 2-substituted methylenecyclopentanes and methylenecyclohexanes based on the allylboration of carbonyl compounds and alkoxyacetylenes with 1-(dialkylborylmethyl)cyclopentene and -cyclohexene is described.
Bubnov, Yuri N.,Lavrinovich, Larisa I.
p. 4551 - 4554
(2007/10/02)
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