Secondary mesylate

The iodo derivative is a useful intermediate for the preparation of a wide variety of different types of compounds. Primary mesyl esters also react with sodium iodide in acetone, but the selectivity of this cleavage is less because of the greater reactivity of secondary mesyl esters. oa( ) Methyl 2,3,4-tri-0-acetyl-6-0-mesyl-a-D-glucopyranoside is converted into methyl 2,3,4,6-tetra-O-acetyl-a-D-glucopyranoside with acetic anhydride and potassium acetate. Replacements of a primary mesyloxy group with fluorine by use of potassium fluoride in methanol,106 with chlorine by use of lithium chloride,102 and with pyridine to form a pyri-dinium deoxy derivative,106 have been reported. Primary tosyloxy groups have been replaced by hydrogen,106 by thiocyanate,107 and by... 

If primary and secondary mesylates are present in the substrate, a fluoro-olefination" reaction may take place, as reported for the synthesis of ( )-fluorobotryodiplodin. ... 

Later work showed that such displacements can be effected with a BusSnCu reagent [83], With this reagent secondary mesylates afford allenylstannanes as the exclusive kinetic products (Eq. 68). The configuration of the allenic products was confirmed by an independent synthesis involving an orthoester Claisen rearrangement (Eq. 69). 

The total synthesis of (+)-asimicin, which belongs to the family of Annonaceous acetogenins, was completed by E. Keinan and co-workers. In order to create one of the tetrahydrofuran rings stereospecifically, an intramolecular Williamson ether synthesis was performed between a secondary alcohol and a secondary mesylate using pyridine as the base. 

As base. The 0-alkylation of tetronic acids and the alkylation of 2-pyridone (at O with primary halides and at N with secondary halides) are mediated by CsF. In each case the displacement of secondary mesylates with carboxylic acids and malonic esters proceeds stereoselectively using CsF as the base, thereby permitting the preparation of chiral substances. 

The synthesis of 2-acetamido-1,6-anhydro-2,3-dideoxy-B-D-rlbo-hexopyranose from a 3-thlo-sugar by reductive desulphurization is covered in Chapter 9. Reduction (NaBH ) of secondary mesylates with a vicinally related trans-dlallylamlno group proceeds to give deoxygenated products via aziridinium ion intermediates, sequence, sometimes the product is that of amino migration examples are detailed in Chapter 9. 

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