The generation of uncomplexed phenyl selenide anion and its applicability to SN2 - type ester cleavages

A convenient synthesis of some symmetrical and unsymmetrical diarylmethyl sulfur and selenium compounds: X-ray crystal structure of diphenylmethylseleno-2-propene and bis[p-chlorophenyl(phenyl)methyl] diselenide

“…Dimethyl formamide has been employed as a co-solvent in this reaction. Addition of DMF improves the yield by solubilizing the diarylmethyl chalcogenolate anion, which is otherwise known to exist as boron complex possessing diminished nucleophilicity [10].…”

Synthesis of seleno-carbohydrates derived from d-galactose

“…The use of a more powerful PhSeNa nucleophile, generated from the reaction of (PhSe) 2 with metallic sodium in THF-HMPA, resulted in very low conversion. 44 In all reactions, after prolonged heating, a yellow color was observed in the solution, indicating the reoxidation of the selenide anion back to the diphenyl diselenide. Thus, using the standard conditions followed by addition of an excess of NaBH 4 after 12 h, furnished the best results using the tosylate as leaving group, and the seleno-carbohydrate 3a was obtained in a moderate 68% yield (entry 7).…”

The Total Synthesis of ( - )-Tetrahydrolipstatin

“…To our dismay, all attempts to hydrolyze the methyl ester (14) proved unsatisfactory under a wide range of 3 SiOK, [39] Na/Ph 2 Se 2 , [37] 1 M HCl, high pressure, [40] and a selection of enzymatic procedures based on lipases derived from Pseudomonas, Candida rugosa, and Candida antarctica. [41,42] The failure of the lipase-mediated procedures to effect the transformation was particularly ironic given the biological activity of our ultimate target (1).…”

“…The methyl ester was expected to be more readily cleavable, given the wide range of procedures effective on methyl esters [34] including those based on nucleophilic substitution. [35][36][37] Our synthesis started with diene ester (11), obtained in 76% yield by the Horner-Wadsworth-Emmons [29] coupling of (2E)-4-(diethoxyphosphinyl)butenoic acid, methyl ester, [38] and dodecanal. Formation of the diol (12) and its subsequent conversion to the cyclic sulfites (13) followed the previously developed conditions, and S N substitution using the diorganocuprate reagent derived from n-hexyllithium afforded (14) with an improved 61% overall yield from diene (11).…”