Alcohol into a mesylate

Replacement of a primary or secondary hydroxyl function with deuterium is usually carried out by first converting the alcohol into a mesylate or tosylate ester, which can then be displaced by treatment with lithium aluminum deuteride. The... 

A MECHANISM FOR THE REACTION ] Conversion of an Alcohol into a Mesylate (an Alkyl Methanesulfonate) 516... 

In one example of this type of cyclization aminoalcohol, 288, which was obtained by conjugate addition of racemic 2-(2-hydroxyethyl)piperidine to allyl phenyl sulfone, was converted into the corresponding chloride and cyclized in the presence of LDA to give 289 as a single diastereomer (Scheme 63) <2003JOC9389>. In a related approach, the primary alcohol group was activated for a similar cyclization by transformation into a mesylate <20010L2957>. 

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... 

The TPS group is a sil> 1 protecting group that can be removed using TBAF as a source of fluoride ion. After removing the protecting group the alcohol function is converted into a mesylate, which is transformed in the third step via a Finkelstein reaction into an iodide. 

This alcohol is transformed in the second reaction into a mesylate. 

The transformation of an alcohol into a halide can be done either by substitution of a good leaving group such as mesylate by I (as in this case) or alternatively for example by Appel analog reactions involving PPh3. 

Both enantiomers of a member of the new chiral pool, propylene oxide 44, can be made from lactic acid 33. The idea is to reduce the acid and cyclise in two different ways. One is simple enough. Ethyl lactate 41 is mesylated, to turn the secondary alcohol into a leaving group 42, and then the ester is reduced. Cyclisation uses the primary alcohol of 43 as the nucleophile in an internal SN2 reaction so that inversion gives (R) -propylene oxide15 44. 

A significant amount of work has been focused on the synthesis of benzylic and allylic phosphonates. Historically, popular synthetic routes entailed the conversion of the alcohol into a good leaving group such as a mesylate or a halide followed by conversion to the organophosphorus compound. A more efficient synthesis would entail the direct conversion of the alcohol into the phosphonate. To this end, Wiemer described the use of zinc iodide as a Lewis acid catalyst for the direct conversion of benzylic and allylic alcohols into phosphonates (Schemes 4.51 and 4.52) [104]. Zinc iodide is inexpensive and... 

O-isopropylidene derivative (57) must exist in pyridine solution in a conformation which favors anhydro-ring formation rather than elimination. Considerable degradation occurred when the 5-iodo derivative (63) was treated with silver fluoride in pyridine (36). The products, which were isolated in small yield, were identified as thymine and l-[2-(5-methylfuryl)]-thymine (65). This same compound (65) was formed in high yield when the 5 -mesylate 64 was treated with potassium tert-hx Xy -ate in dimethyl sulfoxide (16). The formation of 65 from 63 or 64 clearly involves the rearrangement of an intermediate 2, 4 -diene. In a different approach to the problem of introducing terminal unsaturation into pento-furanoid nucleosides, Robins and co-workers (32,37) have employed mild base catalyzed E2 elimination reactions. Thus, treatment of the 5 -tosylate (59) with potassium tert-butylate in tert-butyl alcohol afforded a high yield of the 4 -ene (60) (37). This reaction may proceed via the 2,5 ... 

Intermediate 10 must now be molded into a form suitable for coupling with the anion derived from dithiane 9. To this end, a che-moselective reduction of the benzyl ester grouping in 10 with excess sodium borohydride in methanol takes place smoothly and provides primary alcohol 14. Treatment of 14 with methanesulfonyl chloride and triethylamine affords a primary mesylate which is subsequently converted into iodide 15 with sodium iodide in acetone. Exposure of 15 to tert-butyldimethylsilyl chloride and triethylamine accomplishes protection of the /Mactam nitrogen and leads to the formation of 8. Starting from L-aspartic acid (12), the overall yield of 8 is approximately 50%, and it is noteworthy that this reaction sequence can be performed on a molar scale. 

Transformation of bromocriptine free base 2 into water soluble salt -mesylate, is the only way to obtain a suitable therapeutical form. Crystallization of mesylate using alcohol as a solvent in the presence of excess of strong acid, e.g. methanesulphonic acid can induce formation of 12 -0-alkyl-derivative 2. Until now this derivatisation of ergot molecule has been practically unknown. In continuation we developed the preparative method for obtaining these compounds, (using tetrafluoroboric acid as a catalyst) (ref. 20). 

In the second step the enol ether introduced with GrignanI reagent 16 is converted into an aldehyde function. For this purpose the secondary alcohol prepared in the first step is mesylated and thus transformed into a good leaving group. 

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... 

For primary and secondary alcohols, the hydroxyl is best made into a leaving group for elimination reactions by sulfonylation with toluene-para-sulfonyl chloride (tosyl chloride, TsCl) or methanesulfonyI (mesyl chloride, MeS02Cl orMsCl). 

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. 

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