Intramolecular allylation of carbonyl

The trimethylammonium iodide of 2-(dimethylaminomethyl)-3-(trimethylsilyhnethyl)-1,3-butadiene is a useful reagent for the introduction of both electrophile and nucleophile. Treatment with lithium enolate in the presence of Pd(PPh3)4 catalyst gives the allylated cyclopentanone, and subsequent intramolecular allylation of carbonyl group in the presence of B114NF gives vicinal exocyclic alcohol (Scheme 5). ... 

Nokami, J. Wakabayashi, S. Okawara, R. (1984) Intramolecular allylation of carbonyl compounds. A new method for five and six membered ring formation, Chem. Lett., 869-70. 

It is proposed that the reaction proceeds through (i) oxidative addition of a silylstannane to Ni(0) generating (silyl)(stannyl)nickel(n) complex 25, (ii) insertion of 1,3-diene into the nickel-tin bond of 25 giving 7r-allylnickel intermediate 26, (iii) inter- or intramolecular allylation of aldehydic carbonyl group forming alkoxy(silyl)nickel intermediate 27, and (iv) reductive elimination releasing the coupling product (Scheme 69). 

Intramolecular allylation of functionalized allylstannanes is feasible. One application used in the synthesis of natural product is shown in Eq. (108) [282]. The yield is, however, moderate in this example. More examples of titanium-promoted inter- and intramolecular reactions of allylstannanes with carbonyl and related compounds are summarized in Table 10. 

A Ti/Pd bimetallic system catalyses allylation of carbonyl compounds, using allyl carbonates, and is particularly useful for ketones that are reluctant participants in many allylation protocols. Stereoselective intramolecular versions are also described. ... 

The aqueous indium-mediated allylation of carbonyl compounds could also proceed intramolecularly, as described in carbocyclizations yielding five-, six- and seven-membered rings, which further cyclized to give fused a-methylene-y-lactones ... 

Intramolecular allylation of oxocarbenium ions with allylsilanes is valuable for stereoselective synthesis of cyclic ethers. Allylsilanes (15a-c), bearing a hydroxy or trimethylsiloxy group, are convenient reagents for this cyclization. The (la)-promoted reactions of (15a-c) with carbonyls or acetals efficiently afford cyclic... 

Samarium(II) iodide in the presence of Pd(0) can also promote this transformation. An example is the transformation of 5-alkenylpyranoside 106 into homoallyl cyclopentanols 107 (82% yield) and 108 (12% yield) [80], The first step is the formation of an allenylpalladium complex, followed by reduction by Sml2 and subsequent intramolecular allylation of the originated carbonyl-tethered allenylsamarium (Scheme 3.41). 

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... 

A study of substituent influences on reaction of carbonyl compound (102) with trialkylallyltin (103) has established that high yield of allylation product (104) is obtained only when X = NO2 and R = OH (where R = Bu or Me and R = H or Me). The role of the intramolecular hydrogen bond in promoting rate enhancement and regioselective allylation (and reduction by HSnBus) of carbonyl compounds has been discussed. 

Coupling with allyl acetates gives allyl boronates,14 which exhibit a high diastereoselectivity in the intramolecular allyl boration of carbonyl compounds15 (Scheme 2). 

Other solid-phase preparations of carbonyl compounds include the hydrolysis of acetals (Table 12.4), inter- [52] and intramolecular Pauson-Khand reactions, the isomerization of allyl alcohols, and the a-alkylation and a-arylation of other ketones. Tietze reported the generation of acetoacetyl dianions on cross-linked polystyrene and their selective alkylation at C-4 (Entry 6, Table 12.4). The use of weaker bases resulted in single or twofold alkylation at C-2 [53]. 

Intramolecular interception of the Criegee carbonyl/carbonyl oxide intermediate was observed in the ozonolysis of steroidal allylic alcohols at — 70 °C. In hexane, the 1,2,4-trioxolane 132 (a mixture of ( Vcpimers) was isolated in 26% yield. Reductive workup afforded the hemiacetal of the dioxolane 133 which could be oxidized to the dioxolane-lactone the hydroperoxide 134 can be isolated in other solvents. When the ozonolysis was carried out in ethyl acetate at —78°C, the yield of the dioxolane-hemiacetal 133 was 95% (Scheme 51) <1990J(P1)1220>. 

Several indium-mediated intramolecular carbonyl allylation reactions have been investigated, and it has been found that these reactions provide an easy access to a variety of cyclic compounds. The intramolecular cyclization of 49a-c mediated by indium in aqueous media proceeds smoothly to afford carbocyclic systems containing y-hydroxy-Q -methylene esters 50a-c, which either spontaneously or readily cyclize to give fused o -methylene-y-butyrolactones 51a-c (Scheme 52). The same cyclization of 49d is too slow to compete with the side-reaction, in which the bromide is substituted by a hydroxy group. The ring junction stereochemistry of fused lactones 51 has been found to be cis in all cases. Of the two possible transition states, the one leading to the m-fused compounds is preferred, because the chair-chair conformation is favored over the chair-boat conformation.209... 

Intramolecular condensation of 197 gave 198, which then aromatized to 119. Alternatively, tautomerization of the allylic amine 195 involving the C-6 carbonyl followed by rotation of the C(5)-C(5a) bond and isomerization gave 197 (Scheme 34) <1998JOC1290>. 

A review about the rearrangement and cycloaddition of carbonyl ylides generated from a-diazo compounds is available <2001CSR50>. Enantioselective intramolecular cyclopropanations of allyl 2-diazo-3-silanyloxybut-3-enoates to yield cyclopropyl 7-butyrolactones have been investigated with a variety of chiral rhodium catalysts. The best results were obtained with Rh2(PTTL)4, where enantioselectivity culminated at 89% ee (Equation 99) <2005TA2007>. 

Sato and coworkers [137] reported the synthesis of macrocyclic lactones via intramolecular alkylation of n-allylic nickel complexes, based on the facile reactivity of n-allylic nickel complexes toward alkyl halides. As shown in Scheme 75, this method was applied to the synthesis of the macrolide recifeiolide 227). The linear precursor 226 in benzene was added slowly over 1 h to nickel carbonyl in benzene at 50 °C. After additional 1.5 h at 50 °C, 227 was obtained in 32% yield. 

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