Allylic sources reacting with

Allylic Sources Reacting with L-C= Y Sinks, Acyiation... 

Cycloaddition of COj with the dimethyl-substituted methylenecyclopropane 75 proceeds smoothly above 100 °C under pressure, yielding the five-membered ring lactone 76. The regiocheraistry of this reaction is different from that of above-mentioned diphenyl-substituted methylenecyclopropanes 66 and 67[61], This allylic lactone 76 is another source of trimethylenemethane when it is treated with Pd(0) catalyst coordinated by dppe in refluxing toluene to generate 77, and its reaction with aldehydes or ketones affords the 3-methylenetetrahy-drofuran derivative 78 as expected for this intermediate. Also, the lactone 76 reacts with a, /3-unsaturated carbonyl compounds. The reaction of coumarin (79) with 76 to give the chroman-2-one derivative 80 is an example[62]. 

Alkenes react with N bromosuccimmide (NBS) to give allylic bromides NBS serves as a source of Br2 and substitution occurs by a free radical mechanism The reaction is used for synthetic purposes only when the two resonance forms of the allylic radical are equivalent Otherwise a mixture of isomeric allylic bromides is produced... 

Substitution. In free-radical substitution, the olefin reacts with a free-radical source to form the allyl free radical, which in turn reacts with available reagent to produce both the final product and a new free radical. 

The following compounds have been obtained from thiete 1,1-dioxide Substituted cycloheptatrienes, benzyl o-toluenethiosulfinate, pyrazoles, - naphthothiete 1,1-dioxides, and 3-subst1tuted thietane 1,1-dioxides.It is a dienophile in Diels-Alder reactions and undergoes cycloadditions with enamines, dienamines, and ynamines. Thiete 1,1-dioxide is a source of the novel intermediate, vinylsulfene (CH2=CHCH=SQ2). which undergoes cyclo-additions to strained olefinic double bonds, reacts with phenol to give allyl sulfonate derivatives or cyclizes unimolecularly to give an unsaturated sultene. - Platinum and iron complexes of thiete 1,1-dioxide have been reported. 

The metal catalyst is not absolutely required for the aziridination reaction, and other positive nitrogen sources may also be used. After some years of optimization of the reactions of alkenes with positive nitrogen sources in the presence of bromine equivalents, Sharpless et al. reported the utility of chloramine-T in alkene aziridinations [24]. Electron-rich or electron-neutral alkenes react with the anhydrous chloramines and phenyltrimethylammonium tribromide in acetonitrile at ambient temperature, with allylic alcohols being particularly good substrates for the reaction (Schemes 4.18 and 4.19). 

The THF-soluble salt tetrabutylammonium fluoride (TBF) is a common source of fluoride. An alternative reagent is tetrabutylammonium triphenyldifluorosilicate (TBAF).115 Unsymmetrical allylic anions generated in this way react with ketones at their less-substituted terminus. 

Silyltitanation of 1,3-dienes with Cp2Ti(SiMe2Ph) selectively affords 4-silylated r 3-allyl-titanocenes, which can further react with carbonyl compounds, C02, or a proton source [26]. Hydrotitanation of acyclic and cyclic 1,3-dienes functionalized at C-2 with a silyloxy group has been achieved [27]. The complexes formed undergo highly stereoselective addition with aldehydes to produce, after basic work-up, anti diastereomeric (3-hydroxy enol silanes. These compounds have proved to be versatile building blocks for stereocontrolled polypropionate synthesis. Thus, the combination of allyltitanation and Mukayiama aldol or tandem aldol-Tishchenko reactions provides a short access to five- or six-carbon polypropionate stereosequences (Scheme 13.15) [28],... 

Besides commonly used TsN=IPh, TsNs can also be employed as a nitrene source. Bach and Korber have recently reported an Fe(iii)-catalyzed imidation of allyl sulfides 200 with iV-/ //-butyloxycarbonyl azide (BocNs), followed by [2,3]-sigmatropic rearrangement (Scheme 21). " The azide reacts with FeCl2 to generate Fe(iv) nitrene complex 201, which then reacts with allyl sulfide 200, to give an intermediate sulfimide 203, presumably through Fe(iii) intermediate 202. 

Esters of allylic alcohols with resin-bound carboxylic acids can be converted into allyl palladium complexes, which react with carbon nucleophiles and with hydride sources to yield the formally reduced allyl derivatives (Entries 3 and 4, Table 3.47). Alkyl sulfonates have been reduced to alkanes with NaBH4 (Entry 5, Table 3.47). Aryl sulfonates (Entry 6, Table 3.47) and aryl perfluoroalkylsulfonates [814] can be reduced to alkanes by treatment with catalytic amounts of Pd(II) and formic acid as a hydride source. 

The action of A-chlorosuccinimide, or a source of positive fluorine such as Selectfluor , in aqueous acetonitrile on the alkene 138 (R1 = Me) is to open the azetidine ring by attack at the allylic position to yield the cyclobuten-3-ol 139 (R OH, R2 = H, R3 = Me) <2003JOC5292>. Chlorosulfonyl isocyanate (CSI) reacts with 138 (R = Et) to give both a chlorobutene 139 (R1 = Cl R2 = CONH2 R3 = Et) and the bicyclic reduced pyrimidone 140 (R1 = Et). However, the action of CSI on the more substituted 2-azabicyclo[2.2.0]hex-5-ene 141 provided the reduced mono-cyclic pyrimidone 142 <2003JOC1626>. 

Morken and Lavastre used the formation of a colored side product to identify catalysts for the allylation of /i-dicarbonyl compounds [8]. The researchers employed 1-naphthyl allyl carbonate 5 as an allyl source and the diazonium salt of fast red as an indicator. Formation of the active 7z>allyl complex furnishes C02 and 1-naphthoxide which deprotonates the 1,3-dicarbonyl compounds which can, in turn, react with the 71-allyl metal complex. 1-Naphthol is the only species in the reaction mixture that can react with the diazonium salt 6 to generate the bright red azo dye fast red. Thus the red color is indicative of successful formation of the active re-allyl complex (Figure 5.4.3). 

Although O2 reacts with proton sources to form HOO- (which dispropor-tionates via a second 02), with limiting fluxes of protons to control the rate of HOO- formation from 02, the rate of decay of HOO- is enhanced by reaction with the allylic hydrogens of excess 1,4-cyclohexadiene (1,4-CHD).25 Because HOO- disproportionation is a second-order process, low concentrations favor hydrogen-atom abstraction from 1,4-CHD. This is especially so for MezSO, in which the rate of disproportionation for HOO- is the slowest (PhCl > MeCN > H20 > DMF > Me O).16... 

A bis(tosyl)amidoruthenium(III) complex has been prepared and characterized by X-ray analysis [40]. This complex was found to react with, e.g., cyclohexene (58) to give the allyl toluene-p-sulfonoamide, 60, in 63 % yield. Furthermore, the reaction was found to be catalytic when Phi = NTs was used as the terminal nitrogen source. 

Heathcook et al. have performed a diastereoselective aza-ene reaction using chiral di-(+)-menthyl diazenedicarboxylate 91 as the nitrogen source [54]. Compound 91 was found to react with various alkenes in the presence of 2 equiv. SnCl4, and the corresponding allylic aminated product was obtained in good yield and with de up to 42 %. The problem with this approach was the removal of the chiral menthyl ester auxiliary, which was found to be rather difficult. 

Addition of an electrophile (see Electrophile) to metal-bound cyanides will often form an isocyanide ligand (see Electrophile), -CsN-R. For example, the compound [Fe P(OMe)3 (NO)2(j7 -C3H4R)], which is a source of the allyl cation ( -C3H4R)+, reacts with trans-[Mn(CN)(CO)(dppm)2] to alkylate the cyanide, giving an allyl isocyanide ligand (equation 8). The tungsten alkyne... 

In the preparation of 7r-allyl complexes from cychc allylic chlorides, the stereochemistry of chloride displacement has been found to depend on the reaction conditions (Scheme 27). When the allylic chloride (17) is reacted with Pd2(dba)3, the product from syn oxidative addition, (18)-trans, predominates in nonpolar solvents, while polar solvents give the product from inversion, (18)-c/i. When the Pd(PPh3)4 complex is used as the source of Pd , the isomer from anti addition is isolated in essentially quantitative yield. Apparently, more powerfrd donor solvents or ligands favor anti attack. 

The origin of the initial Ni-H species in the catalysis is a source of speculation. It has been suggested that the ( / -allyl)Ni precursors react with insertion of an ethylene molecule followed by f3-W transfer (e. g., eq. (5)), while in the case of the zerovalent nickel species the ethylaluminum component could react directly either with alkyl transfer or with an intermediate Ni(CH2Cl)Cl species formed by the oxidative addition of dichloromethane, e.g., eq. (6) [3, 5, 6]. Related organopalladium compounds, e. g. ClCH2Pd(Cy2PC2H4PCy2)Cl, have been characterized by X-ray diffraction [54-56]. 

Allyltin compounds are useful in organic synthesis as a non-basic source of a weakly nucleophilic allyl group. Electrophiles usually react in a y-anti (Se2 ) sense, which involves allylic rearrangement. (Some multiply-bonded electrophiles such as SO2 and aldehydes are exceptional in that they react with. s vn-stercochemistry, but these reactions are perhaps better regarded as ene-reactions, and are considered as such in Section 9.1.3.4). Thus the acidolysis of a mixture of methylcyclohepten-2-ylstannanes proceeds as shown in equation 9-16. 46 Reactions of this type can be used for the allyhc isomerisation of terpene hydrocarbons, for example of (+)-a-pinene into (+)-P-pinene (equation 9-17).47... 

---