Allyl acetates synthesis

Simple esters cannot be allylated with allyl acetates, but the Schiff base 109 derived from o -amino acid esters such as glycine or alanine is allylated with allyl acetate. In this way. the o-allyl-a-amino acid 110 can be prepared after hydrolysis[34]. The Q-allyl-o-aminophosphonate 112 is prepared by allylation of the Schiff base 111 of diethyl aminomethylphosphonates. [35,36]. Asymmetric synthesis in this reaction using the (+ )-A, jV-dicyclohex-ylsulfamoylisobornyl alcohol ester of glycine and DIOP as a chiral ligand achieved 99% ec[72]. 

Intramolecular amination with allylic acetates is used for the synthesis of cyclic alkaloids 175]. Cyclization of 293 affords the six-membered ring compound 294 rather than a four-membered ring. The reaction is particularly... 

Organoboranes are reactive compounds for cross-coupling[277]. The synthesis of humulene (83) by the intramolecular cross-coupling of allylic bromide with alkenylborane is an example[278]. The reaction of vinyiborane with vinyl-oxirane (425) affords the homoallylic alcohol 426 by 1,2-addition as main products and the allylic alcohol 427 by 1,4-addition as a minor product[279]. Two phenyl groups in sodium tetraphenylborate (428) are used for the coupling with allylic acetate[280] or allyl chloride[33,28l]. 

Schemes 28 and 29 illustrate Curran s synthesis of ( )-hirsutene [( )-1]. Luche reduction58 of 2-methylcyclopentenone (137), followed by acetylation of the resulting allylic alcohol, furnishes allylic acetate 138. Although only one allylic acetate stereoisomer is illustrated in Scheme 28, compound 138 is, of course, produced in racemic form. By way of the powerful Ireland ester enolate Clai-sen rearrangement,59 compound 138 can be transformed to y,S-unsaturated tm-butyldimethylsilyl ester 140 via the silyl ketene acetal intermediate 139. In 140, the silyl ester function and the methyl-substituted ring double bond occupy neighboring regions of space, a circumstance that favors a phenylselenolactonization reac-...

The synthesis of 10 features the SN2 displacement of the allylic acetate with migration of R2 from the ate complex6. Precursors 9 are prepared by the hydroboration of 3-acetoxy-l-alkynes that are available with very high enantiomeric purity via the asymmetric reduction of the corresponding l-alkyn-3-ones, and a substantial degree of asymmetric induction occurs in the conversion of 9 to 10. Best results, based on the enantioselectivity of reactions of 10 with aldehydes, are obtained when R2 is a bulky group such as isopinocampheyl (79 85 % ee)6. The yields of reactions of 10 with aldehydes are 62-76%. 

Allylsilanes are available by treatment of allyl acetates and allyl carbonates with silyl cuprates17-18, with antarafacial stereochemistry being observed for displacement of tertiary allyl acetates19. This reaction provides a useful asymmetric synthesis of allylsilanes using esters and carbamates derived from optically active secondary alcohols antarafacial stereochemistry is observed for the esters, and suprafacial stereochemistry for the carbamates20,21. 

When the Pd bears chiral ligands, these reactions can be enantioselective. TT-Allylmolybdenum compounds behave similarly.Because palladium compounds are expensive, a catalytic synthesis, which uses much smaller amounts of the complex, was developed. That is, a substrate such as an allylic acetate, carbo-... 

The Stille reaction has been successfully applied to a number of macrocyclic ring closures.207 In a synthesis of amphidinolide A, the two major fragments were coupled via a selective Stille reaction, presumably governed by steric factors. After deprotection the ring was closed by coupling the second vinyl stannane group with an allylic acetate.208... 

A combination of a Tsuji-Trost and a Michael addition was used for the synthesis of (+)-dihydroerythramine 6/1-269, as reported by Desmaele and coworkers [128]. The Pd-catalyzed reaction of the allylic acetate 6/1-267 with the nitromethylarene 6/1-266 in the presence of Cs2C03 as base led to the domino product 6/1-268 as a 4 1 mixture of two diastereomers in 79% yield. Further manipulation of 6/l-268a yielded the desired dihydroerythramine 6/1-269 (Scheme 6/1.70). Interestingly, using the corresponding allylic carbonate without additional base gave the mono-alkylated product only. 

Allyl acetates are more commonly used as electrophiles for the palladium-catalyzed allylic alkylation than allylic nitro compounds.20 However, the reaction of allylic nitro compounds has found wider applications. Allylic nitro compounds are readily available by nitration of alkenes. The regio- and stereoselective introduction of electrophiles and nucleophiles into alkenes is possible as outlined in Eq. 7.19. In fact, this strategy is applied to the synthesis of terpenoids.21... 

Trost and coworkers have devised a stereocontrolled 1,3-diene synthesis employing a palladium-catalysed decarboxylative elimination procedure from allylic acetates carrying carboxylic acid functionality ji- to the acetate group (equation 18)48. This decarboxylative elimination strategy has been applied to the synthesis of an insect pheromone, codlemone48a and the ethyl ester of vitamin A carboxylic acid (Table 5)48b. 

In 1981, it was demonstrated (70) that anions of nitro compounds can be involved in C,C-coupling with allyl acetates at the allylic carbon atom with the use of metal complex catalysis. For many years, this observation did not come to the attention of chemists interested in the synthesis of cyclic nitronates. However, Trost demonstrated (71) that this process can be used in the synthesis of five-membered cyclic nitronates from olefins (18) containing two acyl groups in the different allylic positions (Scheme 3.21). 

The isomerization of allyl ethers and allyl acetals to vinyl ethers or vinyl acetals, respectively, has found many applications in organic synthesis (Equation (17)). Various transition metal catalysts have been reported in the literature for the isomerization of allyl ethers and allyl acetals. 

For the synthesis of heterocycles, an efficient strategy has been introduced utilizing the dual transition metal sequences (Scheme 6).11,lla The key issue is the compatibility of the two catalyst systems. Jeong et al. studied the one-pot preparation of bicyclopentenone 35 from propargylsulfonamide 33 and allylic acetate.11 This transformation includes two reactions the first palladium-catalyzed allylation of 33 generates an enyne 34 and the following Pauson-Khand type reaction (PKR) of 34 yields a bicyclopentenone 35. The success of this transformation reflects the right combination of catalysts which are compatible with each other because the allylic amination can be facilitated by the electron-rich palladium(O) catalyst and the PKR needs a Lewis-acidic catalyst. Trost et al. reported the one-pot enantioselective... 

Murakami generated 3-tributylstannylindoles in situ (but also isolable) using 3-bromoindole 174, allylic acetates and carbonates, and hexamethylditin [179]. A typical procedure is illustrated for the synthesis of 175. The corresponding 5-bromo analog is allylated to the extent of 59%. 3-Stannylindoles couple smoothly in tandem fashion with 2,3-dibromo-5,6-dimethylbenzoquinone under Stille conditions [180]. 

The synthesis of various allyl derivatives of di-i-butyl iminodicarboxylate 21 from its lithium salt and allyl acetates under Pd(0) catalysis has been described. Rearrangements have been observed in some reactions, e.g. equation 19. The products are cleaved to t-butoxycarbonylamines by trifluoroacetic acid at room temperature dilute hydrochloric acid removes the second protecting group54. 

For the synthesis of primary allylic amines, an allyl acetate, e.g. 175, is treated with the benzhydrylamine 176 (Ar = d-MeOCgFLt) in the presence of a catalytic amount of (Ph3P)4Pd and the product 177 is cleaved to the amine 178 with 88% formic acid186. 

This method can be extended for the synthesis of allyl alkyl ethers from alcohols with allyl acetate. Thus, the iridium cationic complex [lr(cod)2] BFc, catalyzes the allylation of alcohols 71 with allyl acetate 72 to afford allyl ethers 73 (Equation 10.14) [30]. 

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