1,3-disubstituted allylic carbonate

Nickel-catalyzed readion of 1,3-disubstituted allylic carbonates and lithium aryl- and alkenylborates provided a regio- and stereoselective route under mild conditions for the synthesis of the corresponding substitution products [75]. 

Addition to linear 1,1-disubstituted allylic acetates is slower than addition to monosubstituted allylic esters. Additions to allylic trifluoroacetates or phosphates are faster than additions to allylic carbonates or acetates, and reactions of branched allylic esters are faster than additions to linear allylic esters. Aryl-, vinyl, alkynyl, and alkyl-substituted allylic esters readily undergo allylic substitution. Amines and stabilized enolates both react with these electrophiles in the presence of the catalyst generated from an iridium precursor and triphenylphosphite. 

Interestingly, treatment of the allylic carbonate 23, which had proven problematic in the previous study, under analogous reaction conditions with the copper enolate derived from 24 furnished the a,/9-disubstituted ketone. Subsequent ring-closing metathesis furnished the 1,2-cyclohexenes 25a/25b in 75% overall yield favoring the trans-dia-stereomer 25a (2° 1°=30 1, ds=10 l) [14]. Overall, this reaction provides an alternative approach to an exo-selective Diels-Alder cycloaddition, and indicates that a-substituted enolates are even more tolerant nucleophiles than the unsubstituted derivatives. 

Type III (no homodimerization) Acrylonitrile," protected 3° allylamines" Vinyl trialkoxysilanes, vinyl siloxanes 1,1-Disubstituted olefins, " non-bulky trisubstituted olefms, vinyl phosphonates, " vinyl phosphine oxides,phenyl vinyl sulfone, acrylonitrile, 4° allylic carbons (all alkyl substituents), protected 3° allylic alcohols, 7,Aolefm of 2-subst. 1.3- butadienes, 7,Aolefin of electronically deactivated 1.3- butadienes ... 

Type IV (spectators to CM) 1,1-Disubstituted olefms " 1,1-Disubstituted olefms, disub. o ,/ -unsaturated carbonyls, 4° allylic carbon-containing olefins, perfluorinated alkane olefins, 3° allylamines (protected)" Vinyl nitro olefins, protected trisubstituted allyl alcohols, a,/ -olefin of 2-subst. 1.3- butadienes, a,/ -olefm of electronically deactivated 1.3- butadienes ... 

The dienylic cations 44 with cyclopropyl and phenyl groups were also prepared and characterized by the protonation of respective fulvenes74. Other cyclopropyl substituted allyl cations include acyclic 1,3- and 1,4-disubstituted allyl cations 45 and 46. The charge in these cations is localized mainly on the carbon adjacent to the cyclopropyl group. The rearrangement of these cations at higher temperatures was also studied76. 

In contrast to the case of allylsilanes, anodic oxidation of disubstituted olefins provides in general four regioisomeric products because all the allylic carbon-hydrogen bonds can be cleaved. In the case of allylsilane, the cleavage of a C—Si bond takes place... 

The ajf-disubstituted cyclohexane 414 is prepared by intramolecular allylation of 412 to generate 413, and subsequent decarboxylation-allylation. The diallylation reactions of 412 are based on the fact that intramolecular allylation of the /i-kcto ester 412 with the allylic carbonate moiety is faster than decarboxylation of the allyl carboxylate moiety in 412 [179]. 

AUylation. 2,3-Disubstituted indoles are allylated at C-3 by the Pd-catalyzed reaction with an alkyl allyl carbonate. The allyl group of aUyl o-// -nitroarylacetates is recaptured via a sp -sp couphng after decarboxylation. ... 

Sequential Rh-catalysed etherification of the allylic carbonate using the Cu(I) alkoxide derived from the enantiomers of the alkenyl alcohols followed by a RCM occur with excellent regio- and enantiospecificity and lead to cis- and traws-disubstituted dihydropyrans <04AG(E)4788>. 

Other synthetic reactions. Catalyzed elimination of allylic carbonates occurs in the absence of nucleophiles. Alkynediols undergo isomerization and dehydration, furnishing 2,5-disubstituted furans as a result. 1-Carboranyltributyltin adds to aldehydes under the influence of the Pd catalyst to form carbinols. The Pd version of a Pauson-Khand cyclopentenone synthesis is accomplishable in the presence of CO, and actually this version is specially suited for a one-step construction of a -methylenecyclopentenones. ... 

As mentioned above, although some examples of intramolecular MBH reactions have been reported in the literature, this aspect is still in its infancy. Most known reports are based on the cyclizations of combinations of enone-enone, enone-acrylate, enone-aldehyde, unsaturated thioester-aldehyde, enone-allylic carbonate frameworks, etc. More recently, Krafft et al. have developed a novel, entirely organo-mediated intramolecular MBH reaction by using allyl chloride 277 as an alternative electrophile to afford densely functionalized cyclic enones 278. This reaction tolerates modification of the enone and the use of primary and secondary allylic chlorides and generates both five-and six-membered rings in excellent yields. Both mono- and disubstituted alkenes are formed with excellent selectivity in the absence of a transition metal catalyst (Scheme 1.100). ... 

The Overman rearrangement of the disubstituted allylic trichloroace-timidates has also been used in the construction of trisubstituted carbons bearing a nitrogen substituent. For instance, heating a solution of the imidate 71 in refluxing xylene fiimishes the allylic trichloroacetamide 72 in good yield. Compound 72 is a precursor to aminocyclopentanol Ti ... 

Derivatives of Y-hydroxyacetylenic acids, which are useful intermediates in the synthesis of butenolides, are prepared from propiolic acid and ester anions. Alk-2-ynoic and 2-allenic esters are prepared by the oxidation of 3,4-disubstituted 2-pyrazolin-5-ones with lead(iv) tetra-acetate in the absence and presence of BF3 respectively. Py-Unsaturated esters are produced in high yield by the palladium-catalysed decarboxylation-carbonylation of allylic carbonates. Magnesium enolates of esters react with nitriles to give (Z)-3-amino-alk-2-enoates. Enol lactones react with diethyl methoxycarbonylmethylphosphonate to give cyclic unsaturated keto-esters (Scheme 66). ... 

A chiral quaternary carbon center via an addition-rearrangement reaction of 3,3-disubstituted allyl morpholine (61) and benzyloxyacetyl chloride (56) was successfully constructed with 300 mol% of chiral Mgl2 (60) complex, and the corresponding Claisen adduct (62) was obtained in 97% ee and 94 6 syn anti selectivity (Scheme 4.18). 

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