Ester homologation revisited: a reliable, higher yielding and better understood procedure

Total Synthesis of (+)‐trans‐Trikentrin A

“…Having established a reliable procedure to obtain (S)-35, we worked toward its homologation. After achieving good results with a model substrate by using the Kowalski homologation, [28] the relevant conditions were applied to (AE)-34. The required dibromoketone 40 was prepared in good yield.…”

An approach to an asymmetric synthesis of stemofoline

“…The addition of lithiated dibromomethane gave dibromoketone 11, which was converted into ester 9 by treatment with lithium hexamethyldisilazide and butyllithium. 8 Alternatively, ester 10 was taken through to iodide 12 by reduction and reaction of the resulting alcohol with iodine and triphenylphosphine. Iodide 12 was then converted into the required ester 9 by halogen-metal exchange using tert-butyllithium followed by the addition of methyl chloroformate (Scheme 1).…”

Selective Synthesis of 3‐(α,α‐Dibromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one as an Excellent Precursor for the Synthesis of 2‐Substituted 4‐(4‐Hydroxy‐6‐methyl‐2H‐2‐oxopyran‐3‐yl)thiazoles as Antimicrobial and Antifungal Agents

“… succeeded in the selective bromination of DHA into 2 and then synthesis of thiazoles 8 by Method I, there has been great demand to develop some alternative approaches for such syntheses avoiding the use molecular bromine and α‐bromoketones because of several practical problems associated with them. In this context, we and other research groups have earlier shown that α,α‐dibromketones behave analogous to α‐bromoketones in their reactions with certain nulceophiles such as sulfur nucleophile and bidentate nucleophiles containing nitrogen and sulfur atoms . These studies involving α,α‐dibromoketones have offered a valuable modification to the most widely used Hantzsch thiazoles synthesis .…”