Allylic Alcohols as Radical Allylating Agents. An Overall Olefination of Aldehydes and Ketones

Abstract

2-Fluoropyridyl derivatives of allylic alcohols react with xanthates in the presence of lauroyl peroxide to give alkenes, often with high stereoselectivity. If the allylic alcohols are themselves derived from aldehydes or ketones, the overall process becomes a synthetic equivalent of the classical Wittig and related olefination reactions.

Some aspects of radical chemistry in the assembly of complex molecular architectures

“…This constitutes a tremendous synthetic asset and explains the popularity and importance of radical-based methods for the manipulation and modification of oxygen-rich compounds such as carbohydrates and cyclitols. It is, however, possible to transform an alcohol into a leaving group in the radical sense by converting it into a fluoropyridineoxy derivative by reaction of the alkoxide anion with inexpensive 2,6-difluoropyridine [61–65]. In this manner, any allylic alcohol becomes a potential radical allylating agent.…”

2‐Fluoro‐5‐nitrophenyldiazonium: A Novel Sanger‐Type Reagent for the Versatile Functionalization of Alcohols

“…Perspectively, the corresponding alcohols may be obtained under mild conditions and with high yields via methanolytical cleavage of the 4‐nitrophenyl unit as described by Takahashi and Ogasawara [14] . Compounds structurally related to 7 have further been reported to be useful for numerous applications, including allylic alkylation, [15] Claisen rearrangement, [16] and carbonyl olefination [17] . As illustrative examples, the previously prepared allylic ethers 7 a and 7 aj were further converted under Tsuji–Trost conditions [18] to transform 8 a and 8 b into the highly functionalized 1,3‐diketones 9 a and 9 aj in yields of 62 and 88 %, respectively (Scheme 5).…”

A Convergent, Stereoselective Route to Trisubstituted Alkenyl Boronates

“…We discovered that the fluoropyridoxy group, in conjunction with the relative long lifetime of radicals generated from xanthates, can indeed undergo the homolytic -scission (10  12, Scheme 2). 15 This alliance translates into a powerful synthesis of alkenes, as outlined in the lower part of Scheme 2 (9  12). 16…”