Diastereoselective Synthesis of Highly Substituted Five-Membered-Ring Oxygen Heterocycles by Zirconocene-Mediated C-C Coupling Reactions
摘要:
As homoenolate equivalents, zirconocene-1-aza-1,3-diene complexes were used for the first time in stereoselective synthesis. By insertion of an unsymmetrical ketone in the Zr-C σ bond, sterically demanding trisubstituted dihydro- and tetrahydrofuran derivatives were prepared in good overall yields and with high diastereoselectivities (see below).
A new radical cyclization method for the formation of C(sp3)–C(sp3) and C–O bonds via MnO2-promoted alkene carboesterification with anhydrides is developed.
Electroreductive coupling of aromatic ketones, aldehydes, and aldimines with α,β-unsaturated esters: Synthesis of 5-aryl substituted γ-butyrolactones and lactams
作者:Naoki Kise、Yusuke Hamada、Toshihiko Sakurai
DOI:10.1016/j.tet.2017.01.013
日期:2017.2
The electroreductive intermolecular coupling of aromatic ketones and aldehydes with α,β-unsaturated esters in the presence of TMSCl gave the adducts as γ-trimethylsiloxy esters. The detrimethylsilylation of the adducts with TBAF afforded 5-aryl substituted γ-butyrolactones. The electroreductive coupling of N-(4-methoxyphenyl)-1-arylmethaneimines with methyl acrylate in the presence of TMSCl gave the
Direct generation of lithium homoenolates from 3-aryl α,β-unsaturated ketones or esters by an arene-catalysed lithiation: Synthesis of substituted tetrahydrofurans and γ-butyrolactones
作者:Emma Alonso、Diego J. Ramón、Miguel Yus
DOI:10.1016/s0040-4020(96)01155-6
日期:1997.2
The reaction of α,β-unsaturated ketones 1 with an excess of lithium powder, a catalytic amount of naphthalene (4 %) and different carbonyl compounds in the presence of boron trifluoride in THF at −78 – 0°C yields, after treatament with silyl nucleophile and final hydrolysis, the expected substituted tetrahydrofurans 5. Similar methodology applied to β-aryl acrylic esters 6, but without using boron trifluoride
The Reaction of Olefins with Malonic Acid in the Presence of Manganese(III) Acetate
作者:Nobuyuki Ito、Hiroshi Nishino、Kazu Kurosawa
DOI:10.1246/bcsj.56.3527
日期:1983.11
The reaction of 1,1-diphenylethene with malonic acid in the presence of manganese(III) acetate gave 3,3,8,8-tetraphenyl-2,7-dioxaspiro[4.4]nonane-1,6-dione and 4,4-diphenyl-2-(2,2-diphenylethenyl)-4-butanolide. Similar reactions with 1,1-bis(4-methoxyphenyl)ethene, methylenecyclohexane, 2-phenylpropene, 1-octene, and cyclohexene yielded the corresponding 2,7-dioxaspiro[4.4]nonane-1,6-diones.
Oxidative Ring-Opening Reaction of Cyclopropanone Acetals with Carbonyl Compounds via Photoinduced Electron Transfer. Generation of a .beta.-Carbonyl Radical Species and Its Application to the Synthesis of .gamma.-Hydroxy Ester Derivatives
作者:Manabu Abe、Akira Oku
DOI:10.1021/jo00115a022
日期:1995.5
Photoinduced electron transfer (PET) reactions of 2-substituted or 2,2-disubstituted cyclopropanone methyl trialkylsilyl acetals 1a-e,g and 1-siloxy-2-oxabicyclo[3.1.0]hexane (1f) with carbonyl compounds 2 (benzophenone (2a), acetophenone (2b), 2-acetonaphthone (2c), 2-acetylpyridine (2d), 4-acetylbenzonitrile (2e), 2,3-butanedione (2f), and benzoyl cyanide (2g)) were examined in the presence of Mg(ClO4)(2). Carbon-carbon bond coupling products (gamma-hydroxy esters 3 or their derivative butyrolactones 4) between 1 and 2 were formed in good yields. A mechanism is proposed for the product formation which is initiated by the single electron transfer (SET) from 1 to the excited state of 2. The SET generates a transient pair of ion radicals, i.e. a ring-opened sec- or tert-beta-carbonyl radical from 1 and a ketyl radical ion from 2 stabilized by the Mg salt. This realizes a novel type of carbon-carbon bond formation at the sterically crowded beta-position of propanoates.