Esters allylic, also

Pd(OAc)2, TPPTS, CH3CN, H2O, Et2NH, 30 min, 89-99% yield. Deprotection can be achieved in the presence of a prenyl or cinnamyl ester, but as the reaction times increase, these esters are also cleaved.Prenyl carbamates and allyl carbonates are cleaved similarly. 

Allyl carbonate esters are also useful hydroxy-protecting groups and are introduced using allyl chloroformate. A number of Pd-based catalysts for allylic deprotection have been developed.209 They are based on a catalytic cycle in which Pd° reacts by oxidative addition and activates the allylic bond to nucleophilic substitution. Various nucleophiles are effective, including dimedone,210 pentane-2,4-dione,211 and amines.212... 

Imidate esters can also be generated by reaction of imidoyl chlorides and allylic alcohols. The lithium anions of these imidates, prepared using lithium diethylamide, rearrange at around 0°C. When a chiral amine is used, this reaction can give rise to enantioselective formation of 7, 8-unsaturated amides. Good results were obtained with a chiral binaphthylamine.265 The methoxy substituent is believed to play a role as a Li+ ligand in the reactive enolate. 

The mechanism by which the enantioselective oxidation occurs is generally similar to that for the vanadium-catalyzed oxidations. The allylic alcohol serves to coordinate the substrate to titanium. The tartrate esters are also coordinated at titanium, creating a chiral environment. The active catalyst is believed to be a dimeric species, and the mechanism involves rapid exchange of the allylic alcohol and /-butylhydroperoxide at the titanium ion. 

Surprisingly, the mono (allyl) titanium complexes 19 reacted with the imino ester 23c also at the y-position with high diastereoselectivities and gave the unsaturated... 

A number of aromatic dicarboxylate esters were also found to undergo allylation with loss of the silyl group when photolyzed in the presence of allyltrimethylsilane in acetonitrile-methanol175. As illustrated in equation 35 the naphthalene dicarboxylate 339 evidently underwent allylation, but then subsequently underwent photochemical [2 + 2] cycloaddition to give the polycyclic product 340 in other cases the reaction stopped after allylation. 

Allyl acetals,21 and carbamates,17 can be lithiated and quenched with metallic electrophiles at the a-position to provide allylmetals, for example, the allyl boronate 22.21 Allyl and benzyl esters have also been lithiated a to O.22... 

The ate-complexes (34) also react with benzylic halides aroyl chlorides allyl halides and proj r l halides to afford the (x>rr ponding products, respectively (Eq. 75). (E)-a,P-Unsaturated carboxylic esters can also be obtains by the reaction of such borate complexes with ethyl propiolate The same type of reaction between copper(I) methyltrialkylborates and l-(l-pyrrolidinyl)-6-chloro--1-cyclohexene gives the corresponding alkylation products which are readily hydrolyzed to 2-alkylcyclohexanone... 

The oxidative addition of allylic esters is also gaming popularity as a means of deprotecting a carboxylic acid or alcohol (concomitant loss of CO2 from a carbonate). ... 

SnCLrinduced cyclizations between alkenes and enol acetates result in cycloalkanes or bicycloalkanes in high yield (Eq. 59). It is interesting to note that the MesSiOTf-catalyzed reaction can yield fused rather than bicyelo products. Alkenic carboxylic esters, allylic alcohols, sulfones, and sulfonate esters are also cyclized in the presence of SnCU alkenic oxiranes, however, often cyclize in poor yield [89a]. 

The direct transformation of silyl ethers into esters can also be performed by reaction with an acid chloride in CH2CI2 (0 °C to room temperature) in the presence of FeCls (1.5 equiv.) [18]. The formation of allyl ethers from allylic alcohols and methanol is catalyzed by RUCI3 [19]. The reaction is likely to occur via a jr-allyl Ru intermediate. Allylic rearrangements and racemization of optically active allylic alcohols take place. 

Attyl and propargyl group transfer. Sulfinic acids or their sodium salts assist Pd(0)-catalyzed deallylation by accepting the allyl group. In addition to allylic esters, allylic sulfoximines can also deliver the allyl group to nucleophiles such as amines. Acrolein acetals react with 1,3-dicarbonyl compounds but the regiochemistry is strongly dependent on reaction temperatures. ... 

PhMe2Si ethers, sulfonamides, allyl sulfonamides sulfonyl amides, benzyl amides and some esters are also cleaved. ... 

ZrCLi (20 mol % ), CH3CN, rt, 67-92% yield. The groups BOC, Ac, Bz, acetonide, THP, MEM, allyl, prenyl, and Bn were shown to be stable to these conditions, whereas the trityl group is cleaved. PMB esters are also cleaved. ... 

H-(3-zeolite, anisole, toluene, reflux, 1.5-8 h, 70-90% yield. Cinnamyl esters are also cleaved in excellent yield, but allyl esters give mixed results with aliphatic allyl esters showing no cleavage. ... 

Deprotection of allyl groups from carboxylic allyl esters is also possible using these conditions [31, 33]. In a homogeneous CH3CN/H20 medium, the facility of cleavage of the allyl group follows the order allyl > cinnamyl > dimethylallyl. 

Phenylmenthyl esters are also suitable chiral groups for inducing stereoselectivity in radical addition reactions, as shown in the allylation of phenylmenthyloxycarbonyl-substituted xanthates. The photoinitiated reaction of the radical precursor with tributyl(2-propenyl)stannane at — 78 =C affords only one diastereomer4. The absolute configuration of (— )-8-phenylmenthyl 2-methyl-2-phenyl-4-pentenoate (5) is not known. 

Esters. Various esters are obtained by mixing RCHO and alcohols with [(cod)IrCl]2 and K2CO3 at room temperature. In the case of allyl alcohol some propyl esters are also formed. Primary alcohols RCH2OH are oxidized to provide esters RCOOCH2R on heating with [(cod)IrCl]2 in open air (95°). ... 

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