α-Phosphonovinyl Carbanions in Organic Synthesis

Abstract

The generation of several a-phosphono-substituted vinyl carbanions is described. The a-phosphonovinyl carbanions have been used to afford versatile vinylphosphonate reagents capable of a wide range of synthetic transformations.

Michael Additions to Activated Vinylphosphonates

“…The only review covering this area was written by Minami 2 and was published in 1992. Several reviews on vinylphosphonates, [3][4][5] published later on, did not deal with Michael additions. Only very recently was the application of 1-phosphorus-functionalized 1-sulfur-functionalized alk-1-enes in organic synthesis, including their role as Michael acceptors, reviewed.…”

“…The described methodology was also applied to the synthesis of enantiomerically pure cyclopropylphosphonate analogues of nucleotides. 15 The usefulness of vinylphosphonates in the development of a convenient synthetic route to cyclopentanoid frameworks was demonstrated by Minami et al 16,17 who reported the synthesis of tricyclo[6.3.0.0 3,7 ]undecenones 34a-c, which are terpenoids with potential antibacterial and anticancer activity. The starting b-keto vinylphosphonates 29a-c were prepared by the two methods presented in Scheme 7.…”

“…Conversion of 31a-c into the free aldehydes 32a-c and the intramolecular HWE cyclization gave the desired dicyclopent-1-enyl ketones 33a-c in good yield. A polyphosphoric acid catalyzed Nazarov cyclization of these ketones produced the expected tricyclo[6.3.0.0 3,7 ]undecenones 34a-c in moderate yields.…”

“…Minami et al 3 also used a-iodovinylphosphonates as key reagents for the synthesis of highly functionalized enyne compounds containing the phosphono moiety. For example, the palladium-mediated cross-coupling (Sonogashira reaction) of 1-iodo-2-ethoxyvinylphosphonate 164 and 2methylbut-3-yn-2-ol (165) afforded ethyl 1-(ethoxymethylidene)-2-pentynylphosphonate 166, which, after intramolecular addition-elimination reaction followed by hydration of the triple bond, provided vinylphosphonate 167.…”

Highly Selective Preparation of 2-(Hydroxymethyl)vinylphosphonates by Insertion of Ketones into Zirconacycle Phosphonates

“…3 Their preparation is varied. 3,4 Recently, we have shown that it is possible to zirconate 1-alkynylphosphonates 5 with ZrCp 2 Cl 2 -n-BuLi, 6 (1:2) to give three-member phosphonate zircona-cycles. 7 The zirconacycles undergo insertion reactions with alkynes 7 and aldehydes 8 to provide, after hydrolysis, substituted vinyl phosphonates not available by other routes (Scheme 1).…”