Carbonyls allylations

Cope rearrangement 17, 213 f., 643 Corey catalysts 74 f., 80 -, aldol condensations with 74 -, carbonyl allylations with 74 -, carbonyl reductions with 74 f. 

A solid-phase version of the palladium-catalyzed carbonyl allylation of aldehydes by allylic alcohol has been described. Thus, allylation of resin-bound aldehyde (P = Merrifield resin) with allylic alcohols (e.g., MeCH=CHCH2OH) in the presence of SnCl2 afforded the homoal-lylic alcohols under different solvent conditions, in DMSO and aqueous DMSO respectively (Eq. 8.45).102... 

Metal-mediated carbonyl allylation, allenylation, and propargylation of optically pure azetidine-2,3-diones were investigated in aqueous environments.208 Different metal promoters showed varied regioselec-tivities on the product formation during allenylation/propargylation reactions of the kcto-fi-lactams. The stereochemistry of the new C3-substituted C3-hydroxy quaternary center was controlled by placing a chiral substituent at C4. The process led to a convenient entry to densely functionalized hydroxy-ji-lactams (Eq. 8.82). 

Me3SiPdSnBu3 is formed primarily from 6/1-237, which then adds to the allene moiety in 6/1-236 to give a a- or Jt-allyl palladium complex. This undergoes an intramolecular carbonyl allyl addition to afford the cis-cycloalkariols 6/1-238 (Scheme 6/1.61). 

Only a few examples exist for the intermolecular trapping of allyl radicals with alkenes68,69. The reaction of a-carbonyl allyl radical 28 with silyl enol ether 29 occurs exclusively at the less substituted allylic terminus to form, after oxidation with ceric ammonium nitrate (CAN) and desilylation of the adduct radical, product 30 (equation 14). Formation of terminal addition products with /ram-con figuration has been observed for reaction of 28 with other enol ethers as well. 

The chiral ligand (5,5)-Jl, derived from chiral 13., is a controller group that has shown to provide a highly enantioselective version of several powerful synthetic methods, as Diels-Alder, aldol and carbonyl allylation processes. 

Enantioselective carbonyl allylation is one of the most broadly utilized transformations in synthetic organic chemistry (For reviews on enantioselective carbonyl allylation, see [199-204]). Shortly after the first reports of carbonyl allylation employing isolable aUylboron and allylsUicon reagents by Mikhailov and Bubnov [205] and Hosomi and Sakurai [206], respectively, enantioselective carbonyl allylations were reported by Hoffmann (see footnote 19, [207]). While the design of increasingly effective chiral allylmetal reagents continues 207-220], this... 

Fig. 2 Selected examples of chiral allylmetal reagents for enantioselective carbonyl allylation...

For selected examples of catalytic asymmetric carbonyl allylation employing allylmetal reagents, see [221-224]. 

For selected examples of carbonyl allylations employing nucleophilic 7c-allyls derived from allylic acetates and carboxylates, see Palladium [225-233], Rhodium [234, 235], Ruthenium [236-238], Iridium [239-241]. 

For selected reviews on carbonyl allylation via umpolung of 7C-allyls, see [242-247]. 

For catalytic enantioselective carbonyl allylation and crotylation via NozaM-Hiyama coupling, see [248-257]. 

Scheme 8 Carbonyl allylation via hydrogenation and transfer hydrogenation...

As demonstrated in recent work by Obora and Ishii, alkynes serve as allyl donors in carbonyl allylations from the alcohol oxidation level [277]. Specifically, upon exposure to an iridium catalyst generated in situ from [lr(OH)(cod)]2 and P( -Oct)3, l-aryl-2-methylalkynes couple to primary alcohols to furnish homoallylic alcohols with complete branched regioselectivity and excellent levels of diastereoselectivity (Scheme 17). 

Scheme 19 Enantioselective carbonyl allylation from the alcohol or aldehyde oxidation level via iridium-catalyzed C-C bond-forming transfer hydrogenation...

Scheme 20 Carbonyl allylation from the alcohol oxidation level employing isotopically labeled allyl acetate [R = p-(C02Me)C6H4]...

Iterative two-directional chain elongation enables rapid construction of 1,3-polyols (Scheme 23). For example, the polyol substructure that appears in the oxopolyene macrolide (+)-roxaticin is available in nine steps from propane-1,3-diol upon three iterations of double carbonyl allylation [286]. Notably, high levels of catalyst-directed stereoselectivity are observed (For selected examples of catalyst directed diastereoselectivity, see [289-296]). Analogous 1,3-polyol syntheses via iterative homologation in one direction also are reported [297]. 

Scheme 22 1, n-Glycols as dialdehyde equivalents in iridium-catalyzed enantioselective carbonyl allylation from the alcohol oxidation level... 

Allylboron compounds, synthesis, 9, 170-171 5-Allylboron compounds, cross-coupling reactions, 9, 212 Allylboronic esters, synthesis, 9, 194—195 Allyl boryl ethers, isomerization, 10, 88 Allylchlorodimethylsilanes, for carbonyl allylations,... 

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