Cyclopentanone coupling with

Titanium(IV) is a powerful but selective Lewis acid which can promote the coupling of allylsilanes with carbonyl compounds and derivatives In the presence of titanium tetrachlonde, benzalacetone reacts with allyltnmethylsilane by 1,4-addition to give 4-PHENYL-6-HEPTEN-2-ONE. Similarly, the enol silyl ether of cyclopentanone is coupled with f-pentyl chloride using titanium tetrachlonde to give 2-(tert-PENTYL)CYCLOPENTANONE, an example of a-tert-alkylation of ketones. 

As described above, our synthetic strategy involves the convergent construction of the central cyclopentanone ring with a carbonylative cross-coupling reaction and a photo-Nazarov cyclization reaction (Chart 2.2). The electrophilic coupling component 51 was synthesized by an intramolecular Diels-Alder reaction [34] and the nucleophilic coupling component 52 by a vinyiogous Mukaiyama aldol reaction [35]. 

Formation of Silylvinylallenes. Enynes couple with TMSCl in the presence of Li/ether or Mg/Hexamethylphosphoric Triamide to afford silyl-substituted vinylallenes. The vinylallene can be subsequently oxidized to give the silylated cyclopentanone (eq 28). ... 

Then, commercially available o-xylose (471) was treated with cyclopentanone to protect two of the four alcohol groups as acetals. Subsequent tosylation of the primary alcohol function and reduction to a methyl group led to compound 472 in 65% over four steps. In the next step, the xylose derivative was coupled with olefin chloride 470, followed by desilylation and oxidation with Jones reagent to provide the xylose derivative 473. This was coupled with verrucarol (454) and then converted into phosphono ester compound 474 (Scheme 8.19 and 8.20). 

Details of the Janda-Chen synthesis were as follows. A tetrahydropyran (THP) linker was attached to the NCPS support enabling attachment of alcohols via THP ether formation.13 The THP-NCPS resin 1 is derivatized with / -(+)-4-hydroxy-2-cyclopentanone 2, giving the THP ether-based resin 3, followed by coupling of the C13 20 fragment by enone-cuprate addition. The cuprate required was generated from the corresponding E-vinyl stannane 4. The resulting enolate was trapped as the silyl end ether... 

C-Alkyl glycosides are useful carbohydrate mimetics, commonly employed as enzyme inhibitors. The formation of various C-alkyl glycosides was evaluated with phosphates 9 and 12 (Table 3). Mannosyl phosphate 9 was activated with TMSOTf and coupled to allyltrimethylsilane to provide a-allyl glycoside 2 (18) in excellent yield (93%). Coupling of 9 to the cyclopentanone derived trimethylsilyl enol ether 35 afforded 34 as a mixture of diastereomers in 84%... 

Tetraalkyl- and tetraatyl-ethylene glycols (pinacols) are made by reduction of ketones with active metals such as sodium, magnesium, and aluminum. The reaction is only fair for aliphatic and alicyclic ketones. Acetone, methyl ethyl ketone, cyclopentanone, and cyclohexanone all give less than 0% yields of pinacols. Mixtures of ketones are reduced to unsymmetrical pinacols. An active zinc-copper couple has been employed in the reduction of several simple olefinic aldehydes to dieodiols, e.g., crotonaldehyde to dipropenyl glycol,... 

Coupling of an intramolecular nickel-ene process with a methoxycarbonylation shows a striking preference for products with ci5-ielated metal donor (C-1) and acceptor (C-8) sites. ° Thus tricarbonyl(tri-phenylphosphine)nickel (25 mol %), a stable, easy-to-handle solid [compared with the highly volatile and toxic Ni(CO)4], readily catalyzed the conversion of dienyl iodide (278) (THF/MeOH 4 1, 1 atm CO, r.t.) into monocyclic cu-substituted pyrrolidine (280 29%) and the bicyclic cyclopentanone (281 47%, 4 1 isomer mixture) (Scheme 58). ... 

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