Allylation/Methoxycarbonylation

Intramolecular allylation/methoxycarbonylation of alkenes and al-kynes.1 Ni(COD)2 is an efficient catalyst for intramolecular allylation of alkenes (equation I). 

In the case of a sterically hindered allylic methoxycarbonyl group, the epoxida-tion of substituted cyclohexenes-1,4-dienes occurs on the opposite side. Further studies on the epoxidation of j3,7-unsaturated cyclohexenecarboxylic acids and esters indicate that the steric and polar effects of the COaMe group result mainly in anh -epoxidation while the carboxyl group in inert solvent exerts a syn directing effect. ... 

Trost and co-workers have explored asymmetric transidon metal-catalyzed allylic alkyla-dons. Details on this subject have been well reviewed by Trost and others. With the use of asymmetric palladium-catalyzed desymmetrizadon of meso-2-ene-l,4-diols, cii -l,4-dibenzoy-loxy-2-cyclopentene can be converted to the enandometrically pure cii -4-rfirr-butoxycar-bamoyl-l-methoxycarbonyl-2-cyclopentene. The product is a usefid and general building block for synthesis of carbocyclic analogs of nucleosides as presented in Scheme 5.12. 

Allylic oxidation, 25 Aluminum chloride, 28 Amine, dnsopropyl- [2-Propanamine, Af-(l-methylethyl)-], 36 Ammonium, (methoxycarbonylsulfamoyl)-tnethyl-, hydroxide [Ethanaminium, W.W-diethyl-A-t [ (methoxycarbonyl)-amino] sulfonyl] -, hydroxide, inner salt], 41... 

Vinyl sulfones such as 262 are smoothly converted to a,) -unsaturated nitriles such as 263 on treatment with KCN in the presence of dicyclohexyl-18-crown-6 in refluxing t-butyl alcohol (equation 155)148. The reaction conditions are compatible with base-labile functionalities such as a methoxycarbonyl group (equation 156)148. This method can be used in the preparation of the sesquiterpene aldehyde nuciferal from allyl phenyl sulfones. 

Ceric ammonium nitrate promoted oxidative addition of silyl enol ethers to 1,3-butadiene affords 1 1 mixtures of 4-(/J-oxoalkyl)-substituted 3-nitroxy-l-butene and l-nitroxy-2-butene27. Palladium(0)-catalyzed alkylation of the nitroxy isomeric mixture takes place through a common ij3 palladium complex which undergoes nucleophilic attack almost exclusively at the less substituted allylic carbon. Thus, oxidative addition of the silyl enol ether of 1-indanone to 1,3-butadiene followed by palladium-catalyzed substitution with sodium dimethyl malonate afforded 42% of a 19 1 mixture of methyl ( )-2-(methoxycarbonyl)-6-(l-oxo-2-indanyl)-4-hexenoate (5) and methyl 2-(methoxycarbonyl)-4-(l-oxo-2-indanyl)-3-vinylbutanoate (6), respectively (equation 12). 

Alkylation of 2-methoxycarbonyl-l-oxoindane with these sugar-substituted sulfonium salts gives the (/f)-2-alkyl derivatives with enantiomeric excesses up to 12%, while alkylation of ethyl 2-methyl-3-oxobutanoate with allyl or benzyl(aryl)sulfonium perchlorates gives 2-allyl-(or benzyl)-substituted ethyl 2-methyl-3-oxobutanoates 5 with enantiomeric excess up to 25%12. 

R. Bussas, G. Kresze, H. Mmsterer u. A. SchwSbel, Sulfur Reports 2, 215-222 (1983) . .Progress in the Chemistry of Aza Analogs of Sulfur Dioxide" [Allyl-Aminierung mit N,N -Bis(methoxycarbonyl)-schwc-feldiimid (Kresze-Reagenz)]. 

By heating 32 in aqueous dimethyl sulfoxide (DMSO), containing sodium chloride, up to 170°C, loss of a methoxycarbonyl group and then -elimination of acetic acid occur to give alkene 33 in 70% yield. From this, carba-pl-L-mannopyranose 34 has been produced by conversion of the ester group to the hydroxymethyl function, hydroboration, and de-O-protection. Thus, the hydroboration step proceeded by cis-addition anti- to the allylic benzyloxy group. 

A sequential use of two pericyclic reactions involving sulfur compounds is also implied in a general allylic amination of alkenes with Kresze s reagent, 7V,A -bis(methoxycarbonyl)suIfurdiimide (8). A [2,3] sigmatropy, following an ene reaction of the S-allyl sulfinamidine (9) intermediary formed, affords the diamino sulfane (10), easily converted to the carbamate (11) and then to the amine (12) or (13) [511]. The reactions are featured with 2-methyl-2-butene as the alkene to be functionalized. They are described in Organic Syntheses [512]. 

The course of the insertion of diphenylketene into ir-allylpalladium intermediates has been found to depend on the nature of the ir-allyl precursor. Allyl acetates give dienes, while allyl carbonates give car-boxymethylated products (equations 84 and 8S).264 An intermediate allyl Pd—OR species (9) is believed to exist in both cases. When R = Ac, decarbonylation is followed by (J-H elimination, whereas if R = Me, alkoxide attacks the acylpalladium intermediate and yields the methoxycarbonyl compound. 

Intramolecular insertion of alkenes into ir-allylpalladium complexes has been shown to proceed regio-selectively to yield five-membered rings.2621263 TTiis transformation is equivalent to a palladium ene reaction and is completed by a (3-hydride elimination. The C==C bond of ketenes is also capable of undergoing insertion into ir-allylpalladium intermediates.264 The final course of this reaction is dependent on the leaving group in the initial allyl-X precursor. For X = OAc, dienes are observed for X = Me0C02, a methoxycarbonyl adduct is obtained (equation 303).264... 

METHOXYCARBONYL-1,1,6-TRIMETHYL-1,4,4a,5,6,7,8,8a-OCTAHYDRO-2,3-BENZOPYRONE, an intramolecular Diels-Alder reaction is responsible for the diastereoselectivity. The stereoselective 1,4-functionalization of 1,3-dienes is exemplified by a two-step process leading to cis- and trans-1-ACETOXY-4-(DICARBOMETHOXYMETHYL)-2-CYCLOHEXENE. The effectiveness of a silyl hydride in providing a means for erythro-directed reduction of a p-keto amide is applied in a route to ERYTHRO-1 -(3-HYDROXY-2-METHYL-3-PHENYL-PROPANOYLJPIPERIDINE. This is followed by an asymmetric synthesis based on a chiral bicyclic lactam leading to (R)-4-ETHYL-4-ALLYL-2-CYCLOHEXEN-1-ONE. The stereoselectivity with which acetoxy migration can operate to an adjacent radical center is reflected in the one-step reaction that gives rise to 1,3,4,6-TETRA-O-ACETYL-2-DEOXY-a-D-GLUCOPYRANOSE. 

The oxidation of iV-methoxycarbonyl-l,2-dihydropyridine 56 with K 2-chloroperbenzoic acid results in /ra j-dioxygenation of the 5,6-alkene to give the allylic alcohol 57<1998JOC10001> (Scheme 16). The reaction is thought to proceed via an unstable aminoepoxide which is regio- and stereoselectively trapped by m-chloiobenzoic acid. 

Iron complexes can also catalyze allylic amination [31,32]. Enders et al. have demonstrated the nucleophilic addition of various acyclic and cyclic amines to the optically active l-methoxycarbonyl-3-methyl-(T)3-allyl)-tetracarbonyliron cation 49 formed in high yield from reaction of 48 with iron carbonyls. Oxidative removal of the tetracarbonyliron group by reaction with CAN gives 50 with high optical purity and retention of the stereochemistry (Eq. (12)) [31]. The reaction proceeds well for the different amines, and has been used for the synthesis of a compound showing cytotoxic activity against diverse cell lines [31b]. 

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