Ketones, allyl vinyl synthesis

For cycloheptatriene and a series of its derivatives various thermal unimolecular processes, namely conformational ring inversions, valence tautomerism, [1,5]-hydrogen and [l,5]-carbon shifts, are known. An example of such multiple transformations was described65 which can provide a facile approach to new polycyclic structures by a one-step effective synthesis (yields up to 83%) of the two unique ketones 156 and 157. The thermolysis of the neat ether 151 at 200 °C for 24 h gives initially the isomeric allyl vinyl... 

Substituents X and Y based on sulphur are particularly interesting. We have already seen that vinyl sulphides are latent ketones, that allyl sulphides form useful anions and that their sulphoxides give allyl alcohols. Evans17 has used cyclic allyl sulphoxide anions in an allyl alcohol synthesis, and has used the sulphoxide 148 in a Diels-Alder synthesis88 of the hasubanan derivative 149. 

Inaba, S. and Rieke, R. D. 1985. Metallic nickel-mediated synthesis of ketones by the reaction of benzylic, allylic, vinylic, and pentafluorophenyl halides with acid halides. /. Org. Chem. 50 1373-1381. 

Dimethyl diazomethylphosphonate allows the generation of a variety of aldehydic enol ethers and enamines from aliphatic ketones with this single reagent [equation (5)]. " Of particular interest is the direct synthesis of allyl vinyl ethers via the Wittig reaction. ... 

Two new routes to allyl vinyl ethers, suitable substrates for Claisen rearrangement, are summarized in Scheme 41 and equation (22) one involves copper-catalysed solvolytic cleavage by an allylic alcohol of (E)-alkenylpentafluorosili-cates available from hydrosilylation of alkynes," and the other is based on the base-promoted reaction of dimethyl diazomethylphosphonate with aliphatic ketones in the presence of an allylic alcohol." Electrolytic synthesis of allylic ethers direct from alkenes has been discussed earlier in this Report (Scheme 11). ... 

The one-pot Barbier-type addition of alkenyl, aryl, allyl, vinyl, propargyl, alkynyl, or allenylchromium compounds to aldehydes or ketones is known as the Nozaki-Hiyama-Kishi (NHK) reaction. An excellent review by Furstner published in 1999 detailed the exhaustive literature on the carbon-carbon bond formations involving organochromium(III) reagents. This chapter will present major developments and examples of recent carbon-carbon bond formation methodology and improvements as well as their use in natural products synthesis since 1999. 

Entries 11 to 13 are examples of iminium ion and acyliminium ion reactions. Note that in Entries 11 and 12, vinyl, rather than allylic, silane moieties are involved. Entries 14 and 15 illustrate the synthesis of (3,-y-unsaturated ketones by acylation of allylic silanes. 

Several examples of transition metal catalysis for the synthesis of piperidines appeared this year. Palladium catalyzed intramolecular urethane cyclization onto an unactivated allylic alcohol was described as the key step in the stereoselective synthesis of the azasugar 1-deoxymannojirimycin . A new synthetic entry into the 2-azabicyclo[3.3.1]nonane framework was accomplished through a palladium mediated intramolecular coupling of amine tethered vinyl halides and ketone enolates in moderate yields . A palladium catalyzed decarboxylative carbonylation of 5-vinyl... 

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