Allyl lactate

ALLYL LACTATE (Lactic acid, allyl ester) 

The lactic acid used was the commercial edible grade and was almost colorless. The checkers used 635.6 g. of 85% lactic acid, u s.p. The lower grades of commercial acid probably would give somewhat lower yields. 

A suitable piece of apparatus is listed in Catalog LP-24, p. 43 (1944), of the Coming Glass Works. 

Generally, about 35 ml. of water per mole of 80% lactic acid is obtained at this stage, and 4 6 hours of refluxing is required for its removal. The linear lactic acid polymer thus produced contains appro.ximately 3 lactic acid units. 

A large excess of alcohol is essential for a high jueld of ester. Thus, when the ratio of alcohol to acid is 4 1, the yield is 90% when it is 3 1, the yield is 85-88% when it is 2 1, the yield is about 65% and when it is 5 3, the yield is 58-60%. 

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Allyl lactate is a clear, colorless, mobile liquid boiling at... 

Allyl lactate has been prepared by the repeated treatment of lactic acid or its polymer with allyl alcohol in the presence of mineral acid. ... 

Allyl alcohol, 26, 4 Allyl bromide, 25, 49 Allyl chloride, 24, 97 27, 7 Allyl cyanide, 24, 96, 97 Allyl ether, 26, 5 Allyl lactate, 26, 4 Alumina, activated, 23, 25 regeneration of, 23, 25 Aluminum, commercially pure (2S), 21, 9... 

Takano et al. used the Ireland-Claisen rearrangement of an allyl lactate in the total synthesis of calcitriol lactone (Scheme 4.76) [74]. The rearrangement proceeded with a 6.7 1 diastereoselectivity via O-silylation of the intermediate li-che-lated Z-enolate. Takano noted that the corresponding benzyl ether gave significantly lower de (70%) than the PMB ether. This is presumably due to the PMB ether s greater Lewis basicity and hence its greater propensity to coordinate a lithium cation. 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or allyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propane tricarboxylic acid by oxidation of /3-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog. nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of oi-methyl-o -oxalosuccinic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-succinaldehyde dioxime from the ammonium salt of a-methyl-butyric acid by oxidation with. hydrogen peroxide from /9-methyllevulinic acid by oxidation with dilute nitric acid or hypobromite from /J-methyladipic acid and from the decomposition products of glyceric acid and pyruvic acid. The method described above is a modification of that of Higginbotham and Lapworth. ... 

Allylic methyl group hydroxylation and oxidation to carboxylic acid Beauveria bassiana) Allylic methyl group hydroxylation and lactate ester formation glucosidation Cunninghamella echinulata)... 

The construction of the heterocycle 3 started with enantiomerically-pure ethyl lactate. Protection, reduction and oxidation led to the known aldehyde 6. Chelation-controlled allylation gave the monoprotected-diol 7. Formation of the mixed acetal with methacrolein followed by intramolecular Grubbs condensation then gave 3. The dihydropyran 3 so prepared was a 1 1 mixture at the anomeric center. 

Optically active amino acids The NCS-promoted rearrangement of allylic phenyl selenides (12,121) when applied to an optically active substrate (1), available from ethyl (S)-lactate, results in an allylic amine (2), which can be converted into an optically active N-protected D-amino acid (3) in 78-84% ee. 

The dry sodium salt of 5-methyloxazolidine-2,4-dione, obtained from 4.6 parts of sodium, 100 parts of ethanol, 12 parts of urea and 23.6 parts of ethyl lactate, is suspended in 100 parts of dry benzene and 30.25 parts of allyl bromide are added. The mixture is boiled under reflux for 20 hours and the benzene decanted or filtered from any solid. The solution is washed with... 

A Lewis acid-base complex, TiCl4-SbPh3, mediates the allylation of 2-(benzyloxy)propanal with allyltributyl-stannane, where a homoallyl alcohol is obtained with a high yy/z-selectivity (Equation (5)).40 The same complex is also effective for Diels-Alder reaction of an acrylate of (A)-ethyl lactate with cyclopentadiene, where an endo-adduct is formed predominantly with high diastereoselectivity and without polymerization of cyclopentadiene (Equation (6)). 

With the same length of the tether, the replacement of a butenyl lactate by M allyl 3-hydroxy propanoate 127 led to comparable or lower diastereoselectivitiJ (Scheme 29). J... 

Rearrangement of optically active allylic selenides98 2, derived from enantiomerically pure (S)-lactate and subsequent oxidative cleavage of the double bond, leads to D-amino acids 4 with 78-84% ee. The loss of optical purity is the result of difficulties in synthesizing enantiomerically and diastereochemically pure allylic selenides with Z configuration, rather than the result of incomplete chirality transfer of the rearrangement. 

This zinc-promoted reaction has been used with a variety of carbonyl compounds. Thus, the Luche conditions were applied in a synthesis of (-1-)-muscarine using an aldehyde derived from ethyl lactate [109]. Allyl halide condensation onto a-ketoamides of proline benzyl ester gave good diastereoselec-tivity when performed in the presence of zinc dust and pyridinium p-toluene-sulfonate in a water/THF mixture. In this way, a-hydroxy ketones were obtained with good enantioselectivity after removal of the chiral auxiliary [110]. Reactions of allyl bromide under the Luche conditions with y-aldo esters afforded y-hydroxy esters, which were converted in a one-pot reaction to y-allyl-y-butyro-lactones (Scheme 22) [111]. 

Most of the examples in this chapter have been disubstituted alkenes, a few have been trisubstituted, but none so far has been tetrasubstituted (except cyclic alkenes) as this is the most difficult case of all. One solution49 starts with ethyl lactate 228 and uses a HWE reaction on the enantiomerically pure phosphonate 229 to make the / -enone 230 with very high selectivity. Chelation-controlled addition of a Grignard reagent gives the stereochemically pure allylic alcohol 231. Chelation control is explained in chapter 21. 

In the acyclic series allyl sulfides 6-8, prepared from commercially available (—)-methyl (5)-lactate in several steps via 5, all rearrange with at least 95-98% chirality transfer. Exclusive sulfur migration is observed in the rearrangement of 7 and 8, although both allylic sulfur and allylic oxygen are in the same molecule and can compete for dichloroketene429. 

Allylstannanes undergo similar reaction with a-alkoxy aldehydes under Lewis acid catalysis. The treatment of 464 with allyl tri- -butylstannane in the presence of either MgBr2 Et20 [150] or lithium perchlorate-diethyl ether [153] furnishes protected syn-dio 468 with a dia-stereoselectivity of at least 25 1. This intermediate has been carried on to TBS-protected L-( — )-rhodinose (302) in an overall yield of 46% starting from (9-benzyl ethyl lactate 271b [150] (Scheme 69). 

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