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Horner-Emmons olefination

A 24-analog hydroxystilbene library 34 was constructed from the Horner-Emmons olefination of four resin-bound hydroxybenzaldehyde BBs 33 and six different benzyl phosphonate anions [32], Screening for activity in a cell-based estrogenic assay identified several analogs such as 35 with IC50 values in the 5-15 pM range. [Pg.85]

Diethyl phenylselanylmethanephosphonate can be metalated with n-BuLi in THF at -78°C. The lithiated phosphonocarbanionic species led to the corresponding a-chloro-a-phenylselanylphosphonate after treatment with carbon tetrachloride [61] (Scheme 47). The carbanion derived from the ethyl a-chloro-a-selanylphosphonate was used in a Horner-Emmons olefination with ketones to give a-chlorovinylphenyl selenides. [Pg.135]

Stable but as with the imidazolide it may be protected as the TBS ether to improve its stability. The pyrrole carbinol is sufficiently stable as the lithium salt that aryl halides may be metalated with BuLi. These derivatives may also be converted directly to a,P-unsat-urated esters using the Wadsworth-Horner-Emmons olefination using the Masamune-Roush protocol. Deprotection is accomplished with catalytic DBU or NaOMe. ... [Pg.522]

Reaction with aldehydes or ketones (such as benzaldehyde) in the presence of base gave the olefination product 556 (in 84% yield).502 These variations have come to be called the Horner-Wadsworth-Emmons modiflcation of the Wittig reaction, or Horner-Wadsworth-Emmons olefination.503 It is sometimes called Horner-Emmons olefination. [Pg.665]

The preparation of the C33-C35 segment [137] began with the Horner-Emmons olefination of wo-butyraldehyde, reduction, and asymmetric epoxida-tion [39] leading to epoxy alcohol 234 (Scheme 33). Dithiane epoxide ring opening (regioselectivity 12 1), primary alcohol reduction, and secondary alcohol protection completed the synthesis of this segment ( 235). [Pg.175]

The mechanism of the Horner-Emmons olefination resembles that of the Wittig reaction via betaine intermediates (Scheme 5), and is shown in Scheme 7 for the reaction of a phos-phonate 23 with an aldehyde 27. [Pg.88]

The simplest preparation of the C3o-ester 1 is by Horner-Emmons olefination of 507 with the Cs-ester 67 [75]. Similar results are obtained by Wittig olefination of 507 with the triphenyl-phosphonium bromide corresponding to 67 [76]. Sodium ethoxide has proved suitable as a base in the ethanol/heptane solvent system. The desired product crystallizes out during the reaction. Thermal isomerization yields a second crystal fraction from the mother liquor. [Pg.280]

Dual pathways are available for the reaction of phosphonate anions with a,/ -enones (55). The Michael addition is frontier orbital-controlled and is favored by the presence of proton sources, which quickly neutralize the charge on the enolate anions. These products decrease with time because they are gradually channeled into the charge-controlled Horner-Emmons olefination. [Pg.96]

Floreancig completed the total synthesis of (+)-dactylohde via a sequential Peterson olefination and an intramolecular Hosomi-Sakurai-Prins cycli-zation of the acetal-linked substrate (Scheme 32). Macrocychzation was performed by Horner-Emmons olefination as Smith did (Sect. 3.2.1). The key element of 2,6-cfs-tetrahydropyran in 155 was constructed via the sequential cyclization starting from acetal 156, which involved aldehyde 157 and 1,3-diol 158, synthesized via Denmark s asymmetric aldol reaction and Stille coupling. [Pg.169]

The synthesis of ketone 242 commences with the enantioselective addition of sUyl dienolate 237 to crotonaldehyde 236 catalyzed by Carreira s asymmetric complex [101] to give adduct 238 in 91% ee and 42% yield, albeit with a susceptibihty towards polymerization. Transesterification, sytt-reduction, protection of the corresponding diol, and reduction of the ester afforded aldehyde 239, which was subjected to Horner-Emmons olefination... [Pg.183]

W. Solodenko, U. Kunz, G. Jas, A. Kirschninga, Polymer-assisted Horner-Emmons olefination using PASS flow reactors pure products without puriflcation. Bioorg. Med. Chem. Lett. 2002, 12, 1833-1835. [Pg.612]


See other pages where Horner-Emmons olefination is mentioned: [Pg.2]    [Pg.45]    [Pg.468]    [Pg.468]    [Pg.1051]    [Pg.327]    [Pg.151]    [Pg.48]    [Pg.144]    [Pg.250]    [Pg.266]    [Pg.160]    [Pg.670]    [Pg.899]    [Pg.900]    [Pg.905]    [Pg.905]    [Pg.87]    [Pg.144]    [Pg.658]    [Pg.470]    [Pg.171]    [Pg.110]   
See also in sourсe #XX -- [ Pg.45 ]

See also in sourсe #XX -- [ Pg.87 ]

See also in sourсe #XX -- [ Pg.10 , Pg.14 , Pg.16 , Pg.18 , Pg.126 , Pg.288 , Pg.441 , Pg.442 , Pg.460 , Pg.490 , Pg.534 , Pg.633 ]

See also in sourсe #XX -- [ Pg.665 ]

See also in sourсe #XX -- [ Pg.96 ]




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