Allylic derivatives allyl esters

Silyl enol ethers are other ketone or aldehyde enolate equivalents and react with allyl carbonate to give allyl ketones or aldehydes 13,300. The transme-tallation of the 7r-allylpalladium methoxide, formed from allyl alkyl carbonate, with the silyl enol ether 464 forms the palladium enolate 465, which undergoes reductive elimination to afford the allyl ketone or aldehyde 466. For this reaction, neither fluoride anion nor a Lewis acid is necessary for the activation of silyl enol ethers. The reaction also proceed.s with metallic Pd supported on silica by a special method[301j. The ketene silyl acetal 467 derived from esters or lactones also reacts with allyl carbonates, affording allylated esters or lactones by using dppe as a ligand[302]... 

Allylic acetates react with ketene silyl acetals. In this reaction, in addition to the allylated ester 468, the cyclopropane derivative 469. which is formed by the use of bidentate ligands, is obtained[303]. Formation of a cyclopropane derivative 471 has been observed by the stoichiometric reaction of the 7r-allylpal-... 

Silyl-derived linker 36 was prepared in three steps from a silyl ether of serine and incorporated for Fmoc/tBu-based assembly of protected gly-copeptide blocks (Scheme 11) [42]. The a-carboxylic acid function of serine was protected as an allyl ester. Deprotection by a Pd(0) catalyst in the presence of dimedone liberated the carboxylic acid in order for subsequent... 

Cyclization of quinoline derivatives 57 in DMSO under the action of Cs2C03 at 85 °C afforded diesters 49 <1995T11125>. No cyclization product could be obtained when a piperazino group was present in 57 (Rz = piperazino). Cyclization in the presence of NaH gave a lower yield. When the potassium salt of 57 was used in the presence of 20 mol% of Cul, the conversion was almost quantitative, but the removal of the last traces of copper was difficult. When allyl ester 57 (R = Et, R1 = allyl, R2 = 4 - 7/-biu o ycarbonyl-l -pipcridinyl) was cyclized in DMSO in the presence of Cul and KOBuc at 50-55 °C for 0.5 h, then 100-105 °C for 6 h, the 3-ester 50 (R = Et, R1 = 4-tert-butoxycarbonyl-l-piperidinyl) was obtained in 32% yield. 

Hydrolysis of allyl ester 201b was performed with diethylamine in the presence of Pd(PPh3)4. The carboxylic acid 201c thus obtained could be amidated with a tryptophan derivative using l-(3-dimethylaminopropyl)-3-ethylcarbodiimide as... 

The synthesis were effected with the appropriate glycosylated derivatives of L-threonine (135 and 136). Selective removal of the allyl ester derivative... 

A wide range of carbon, nitrogen, and oxygen nucleophiles react with allylic esters in the presence of iridium catalysts to form branched allylic substitution products. The bulk of the recent literature on iridium-catalyzed allylic substitution has focused on catalysts derived from [Ir(COD)Cl]2 and phosphoramidite ligands. These complexes catalyze the formation of enantiomerically enriched allylic amines, allylic ethers, and (3-branched y-8 unsaturated carbonyl compounds. The latest generation and most commonly used of these catalysts (Scheme 1) consists of a cyclometalated iridium-phosphoramidite core chelated by 1,5-cyclooctadiene. A fifth coordination site is occupied in catalyst precursors by an additional -phosphoramidite or ethylene. The phosphoramidite that is used to generate the metalacyclic core typically contains one BlNOLate and one bis-arylethylamino group on phosphorus. 

Scheme 6.90 Chiral N-benzoyl-protected a-amino acid allyl esters obtained from 64- and 78-catalyzed asymmetric DKR of racemic azlactones derived from racemic natural nonnatural a-amino acids.

One synthetic route to the damascones starts with an appropriate cyclogeranic acid derivative (halide, ester, etc.). This is reacted with an allyl magnesium halide to give 2,6,6-trimethylcyclohexenyl diallyl carbinol, which on pyrolysis yields the desired l-(2,6,6-trimethylcyclohexenyl)-3-buten-l-one. Damascone is obtained by rearrangement of the double bond in the side-chain [98]. 

Enamines derived from ketones are allylated[79], The intramolecular asymmetric allylation (chirality transfer) of cyclohexanone via its 5-proline allyl ester enamine 120 proceeds to give o-allylcyclohexanone (121) with 98% ee[80,81], Low ee was observed in intermolecular allylation. Similarly, the asymmetric allylation of imines and hydrazones of aldehydes and ketones has been carried out[82]. 

Allyl chloride is used to make intermediates for downstream derivatives such as resins and polymers. Approximately 90% of allyl chloride production is used to synthesize epichlorohydrin, which is used as a basic building block for epoxy resins and in glycerol synthesis. Allyl chloride is also a starting material for allyl ethers of phenols, bisphenol A and phenolic resins, and for some allyl esters. Other compounds made from allyl chloride are quaternary amines used in chelating agents and quaternary ammonium salts, which are used in water clarification and sewage sludge flocculation (Kneupper Saathoff, 1993). 

Alkylation and deprotection of N-protected aminomethylphosphonate esters 6 are shown in Scheme 6. The nitrogen is protected as the imine derived from benzophenone or a benz-aldehyde, and a variety of conditions are used for deprotonation and alkylation (Table 2). The benzaldehyde imine of aminomethylphosphonate can be deprotonated with LDA and alkylated with electrophilic halides (entries 1 and 2). For the best yields, saturated alkyl bromides require an equivalent of HMPA as an additive. 36 Allylic esters can be added to the carbanion with palladium catalysis (entries 3-7). 37,38 For large-scale production, phase-transfer catalysis appears to be effective and inexpensive (entries 8-12). 39,40 ... 

The vinylogous elimination to give alkenylcyclopropanes may also be effected via rt-allyl palladium complexes34,35. The palladium(0)-catalyzed substitution of allylic esters with stabilized carbon nucleophiles via 7i-allyl palladium derivatives stereospecifically proceeds with net retention (double inversion) of configuration. Thus, the chirality of an allylic substrate is transferred to resultant alkenylcyclopropanes in the intramolecular S J/ reaction via 7i-allyl palladiums (equation 21)36,3. ... 

Asymmetric allylation.n The chiral enamine 1, derived from the allyl ester of (S)-proline, when treated with this Pd(0) complex at 25° in various solvents provides (S)-( — )-2-allylcyclohexanone (2) in 80-100% ee, the highest enantio-selectivity being observed in CHC13. 

The alkylation products are synthetically useful because simple subsequent transformations furnishes precursors of important natural products as illustrated in Scheme 8E.23. Simple oxidative cleavage of allylic phthalimide 45 generates protected (5)-2-aminopimelic acid, whose dipeptide derivatives have shown antibiotic activity. The esterification via deracemization protocol is not limited to the use of bulky pivalic acid. The alkylation with sterically less hindered propionic acid also occurs with high enantioselectivity to give allylic ester 116, which has been utilized as an intermediate towards the antitumor agent phyllanthocin and the insect sex excitant periplanone. Dihydroxylation of the enantiopure allylic sulfone gives diol 117 with complete diastereoselectivity. Upon further transformation, the structurally versatile y-hydroxy-a,(f-un-saturated sulfone 118 is readily obtained enantiomerically pure. 

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