Highly Diastereoselective Aldol Reaction of Bicyclo[3.2.1]oct-6-en-3-ones and 8-Oxabicyclo[3.2.1]oct-6-en-3-ones. (E)-Selective conversion into ?-alkylidene ketones
作者:Ingo Stohrer、H. Martin R. Hoffmann
DOI:10.1002/hlca.19930760604
日期:1993.9.22
base-mediated elimination with lithiumdiisopropylamide/N,N,N′,N′-tetramethylethylenediamine (LDA/TMEDA; Scheme 2). The simple α-methylidene ketones 17a and 18a were obtained via oxidation of the phenylselenides 19 and 20, respectively (Scheme 4). The tertiary aldol 27 was synthesized best by treatment of 1,3-diketone 26 with Me4Zr (Table 4). In this fashion, the facile retro-aldol reaction of 27 was
New methodology for the [4+3] cycloaddition reactions: generation of oxyallyl cations from α,α′-diiodoketones under sonochemical or thermal conditions
作者:Angel M Montaña、Pedro M Grima
DOI:10.1016/s0040-4039(01)01671-9
日期:2001.10
A new methodology to perform [4+3] cycloaddition reactions of suitable dienes and 1,3-dimethyl-2-oxyallyl cations is presented. The reaction is carried out starting from commercially available dienes and easy-handling α,α′-diiodoketones, which are reduced by the Zn/Cu couple to generate the oxyallyl cation as intermediate. The reaction is carried out under mild thermal or sonochemical conditions at
Ru(II)-Catalyzed Cycloadditions of 1,6-Heptadiynes with Alkenes: New Synthetic Potential of Ruthenacyclopentatrienes as Biscarbenoids in Tandem Cyclopropanation of Bicycloalkenes and Heteroatom-Assisted Cyclocotrimerization of 1,6-Heptadiynes with Heterocyclic Alkenes
derivatives, furnishes the 1:2adducts between the diynes and two molecules of the bicycloalkenes together with common [2 + 2 + 2] cyclocotrimerization products. The structure of a representative tandem 1:2adduct between dimethyl dipropargylmalonate and 2,4-dimethylbicyclo[3.2.1]oct-6-en-3-one was unequivocally determined by X-ray analysis and was concluded to involve an unusual 1,2-dicyclopropylcyclopentene
Facile Synthesis and Ring-Opening Cross Metathesis of Carbo- and Heterocyclic Bicyclo[3.2.1]oct-6-en-3-ones Using Gaseous Olefinic Reaction Partners
作者:Marko D. Mihovilovic、Birgit Grötzl、Wolfgang Kandioller、Radka Snajdrova、Adél Muskotál、Dario A. Bianchi、Peter Stanetty
DOI:10.1002/adsc.200505375
日期:2006.3
were prepared by a facile [4+3]-cycloaddition strategy involving sonochemistry. The oxyallyl species required for the reaction with the corresponding diene was generated from a suitable perbromo ketone with activated zinc under sonification conditions. The resulting dibromo bicyclo compounds were reduced to the target products using a Cu/Zn couple. Ring-openingcrossmetathesis of the resulting bicyclic
Generation of Oxyallyl Cations by Reduction of α,α′-Diiodoketones Under Sonochemical or Thermal Conditions: Improved Methodology for the [4C(4π;)+3C(2π;)] Cycloaddition Reactions
作者:Angel M. Montaña、Pedro M. Grima
DOI:10.1081/scc-120015712
日期:2003.3
An improved methodology to carry out [4C(4pi)+3C(2pi)] cycloaddition reactions of dienes and oxyallyl cations, is presented. The reaction starts from commercially available dienes and easy-handling alpha,alpha-diio-doketones, which are reduced by Zn (powder) or Zn/Cu couple to generate an oxyallyl cation as an intermediate. The reaction is carried out under mild thermal or sonochemical conditions at low tempera tures (from 0 to -44degreesC) and for short reaction times (< 15 min).