Allylic alcohol mesylation

The combination of the preceding method of obtaining allyl alcohols with the Sharpless kinetic resolution (SKR) of secondary allyl alcohols allows conversion of the original racemic allyl alcohol into a pure enantiomer with a 100% theoretical yield. By this procedure, the glycidol obtained by the SKR epoxidation of the secondary allyl alcohol is converted into the corresponding mesylate and then treated with the Te ion, furnishing the allylic alcohol with the same configuration of the enantiomer in the SKR which... 

When the allylic alcohol is the desired product of the kinetic resolution process, the accompanying epoxy alcohol also may be converted to the desired allylic alcohol by the two-step sequence shown in Scheme 6A. 1. The epoxy alcohol, after separation from the allyl alcohol, is mesylated and then subjected to reaction with sodium telluride, which effects the transformation of epoxy mesylate to the allylic alcohol with inversion at the asymmetric carbinol center [ 115e]. Preliminary results suggest that the rearrangement follows this pathway only when the epoxy alcohol is unsubstituted at the 3-position. 

On another front, the mixture of allylic alcohols 512 and 513 was converted by reaction with methanesulfonic acid anhydride in the presence of triethylamine to a mixture of the corresponding mesylates, which were subjected collectively to methanolysis to afford 514, and none of the allylic ether epimeric at C-3 was isolated. N Debenzylation of 514 followed by a classic Pictet-Spengler cyclization then afforded ( )-buphanisine (361) (208). 

The synthesis of y-fluoroalkylated allylic alcohols and amines like 51 starting with chiral fluorinated allylic mesylates 50 has also been reported (Eq. 3) [134]. In this case, the regiochemistry of the addition is controlled by the substrate and the addition of the nucleophile occurs distal to the fluorinated alkyl chain. 

The combination of the chemistry shown in Scheme 22,100 with the Sharpless kinetic resolution (SKR) of secondary allylic alcohols 46101 provides a method for the conversion of racemic allylic alcohols 46 into a single enantiomer with 100% theoretical yield.102 The reaction of sodium telluride with the mesylate 48 derived from 47 affords 46a. In this way, a single enantiomer of the allylic alcohol 46 is obtained in high yield (Scheme 23).102... 

Indoles can be 3-alkylated by allyl alcohols in the presence of lithium perchlorate and acetic acid 101 is an example (Scheme 42). Pyrrole -alkylation can be achieved with simple alkyl halides [1-bromopentadecane, l-(bromomethyl)-, l-(3-chloropropyl)- and l-(3-iodopropyl)benzenes, 2-(2-bromoethyl)- and 2-(3-bromopropyl)naphthalenes] and mesylates [3-phenylpropyl-, l-methyl-3-phenylpropyl-, 2-(2-naphthyl)ethyl- and 3-(2-naphthyl)propyl methanesulfonates] selectively at C(2) and C(5) positions via reaction in various ionic liquids (e.g., Scheme 43) <20050L1231>. 

Corey and Wollenberg have found it possible to introduce a THP-blocked trans allylic alcohol unit via reaction of 2-cyclopentenone and other cyclic enones with the highly reactive mixed cuprate 28.58 Through hydrolysis, mesylation, and base-promoted cyclization of adduct 29, the vinylcyclopropane 30 was obtained (Scheme 8). Thermolysis at 600 °C caused ring expansion to 31. 

AttyBe chlorides. Allylic alcohols (O.IOmole) are readily converted at 0° into allylic chlorides by treatment with mesyl chloride (0.11 mole) and a mixture of lithium chloride (O.IOmole), dry DMF, and. r-collidine (0.11 mole). A nonallylic hydroxyl group, if present, is converted into the mesylate. 

The tricyclic /3-aminocyclohexenone 234 was obtained via intramolecular photoarylation of the bromo arene derivative 233 (Scheme 40). Enamide 234 was treated with sodium hydride, followed by the mesylate derivative of [(trimethylsilyl)methyl]allyl alcohol, to give the allylated compound 235, which was converted to two allyliminium salts 236 and 237. However, attempts to photocyclize these compounds to tetracyclic derivatives were not successful, in contrast to the results of the earlier studies (Scheme 35) in which the spirocyclic system was easily generated in intermediates not rigidly tethered to the aromatic ring. 

Mesylate was chosen as the leaving group and the epoxy mesylate 9 could be made from the corresponding alcohol 12 and that, in turn, from allyl alcohol 13 by Sharpless epoxidation. 

In fact, allyl alcohol 13 was not used at the start of this synthesis because low ees result if there is no substituent on the alkene trans to the alcohol (R2 in the mnemonic should be something other than H). It is much better here to add a removable group and so the silyl alkene 14 was used instead of 13. The silyl group allowed the isolation of the epoxy alcohol 15 in a much higher yield than was possible using allyl alcohol itself and the ee of 15 was >95%. The alcohol was converted to a mesylate 16. 

Substituted 5-vinyl-2,3-dihydro-1,4-dioxins (150), prepared by dehydration of allylic alcohols (142) with mesyl chloride-triethylamine or thionyl chloride-pyridine, undergo [4 -I- 2] cycloaddition reactions with various dienophiles to give the adducts (151). Exposure of (151), obtained by Diels-Alder reaction with dimethyl alkynedicarboxylate, to l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) followed by acidic hydrolysis affords the highly functionalized diesters (152) <88JOC5672>. 

In the benzo-fused series, 2,3-dihydro-2,3-dimethylene-l,4-benzodioxin (160) was obtained by the route outlined in Scheme 6. The 3-methyl substituted acid (158), obtained by methylation of the dianion of 2-carboxy-l,4-benzodioxin, was esterified and then reduced with lithium aluminum hydride to afford the allylic alcohol (159). The treatment of (159) with mesyl chloride at — 70°C in the presence of triethylamine afforded the required diene (160) in 80% overall yield. The Diels-Alder cycloaddition of the diene (160) with range of dienophiles (dimethyl alkynedicarboxylate, acrylonitrile, diisopropyl azodicarboxylate, methyl vinyl ketone, 2-vinylpyridine, 1,4-benzoquinone) gave, in good yields, the corresponding tricyclic adducts <92TL2965>. 

The stereochemistries were established at the stage of the ketones 38 - 40. The enolizable P-ketoester was m-fused compound 28, and the non-enolizable one (keto-form) was tram-fused compound 24. Reduction of the carbonyl group, mesylation or benzoylation, and then base treatment yielded the corresponding a,P-unsaturated ester in each case. Further reduction afforded the allyl alcohols 29 and 30 (Scheme 6). 

Oxidative methylenation Alkyl halides and mesylates are homologated to alkenes. Similarly, epoxides give allylic alcohols with one more carbon atom. 

Dehydration of allylic alcohols. The method involves treatment of the alcohols with MsCl and EtsN (mesylation), and with i-Pr2NEt in HMPA at 140°C for 10 min. 

An aldol type condensation between the B-aminoester (131) and the aldehyde (130), leading to the allyl alcohol (132), constitutes the basis of a new synthesis of (+)-lysergic acid (134). Mesylation... 

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