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Allylation of Oxygen and Nitrogen Nucleophiles

Stereoselective formation of 3-methylenetetrahydrofuran such as 180 by intramolecular allylation of alcohol with allyl benzoate in 179 was utilized in synthetic studies of the core of amphidinolide [70]. Thus treatment of 179 with Pd(OAc)2 and PPh3 in the presence of Me3SnCl (1 equiv.) and NaH in THF afforded the cA-tetrahydrofuran 180 stereoselectively in 77 % yield. In this reaction, the less reactive hydroxy group was converted to the more reactive tin alkoxide by the reaction of Me3SnCl (1 equiv.) and NaH. [Pg.457]

Tetrahydrofuran formation proceeds with high stereocontrol. Cyclization of (E)-allylic ester 181 proceeded at room temperature with overall retention of configuration to give the 2,5-ci5 -tetrahydrofuran 182 using Pd(PPh3)4 in the presence of neocuprone (2,9-dimethyl-l,10-phenanthroline). On the other hand, overall inversion occurred in the reaction of (Z)-allylic ester 183 to afford the 2,5-trans-tetrahydrofuran 184 with ( )-alkene [71]. [Pg.457]

Formal total synthesis of uvaricin was achieved by applying double cyclization of vicinal diol bis(allylic acetate) to afford bis-THF core selectively using chiral ligand Trost L-1 as a key reaction [72], Thus the cyclization of 185 afforded the diene 186 with two new stereocenters in 97 % yield as a single diastereomer. [Pg.458]

The F-ring of the polyether macrolide halichondrin was constructed by Pd-catalyzed selective monocyclization of 187 and 189. No dicyclization took place due to steric reasons. Desymmetrization of the meso-Aio 187 gave the tetrahydro-fiiran 188 in high yield using Trost L-1 as a chiral ligand, and cyclization of the C2 symmetric diacetate 189 afforded the desired diastereoisomeric tetrahydrofuran 190 [73]. [Pg.458]

In contrast to less efficient allylation of alcohols, allylation of phenols proceeds much more smoothly. In the enantioselective synthesis of (—)-galanthamine by Trost, two Pd-catalyzed reactions were utilized. Asymmetric allylation of the bro-movanillin 191 with the cyclic allylic carbonate 192 gave the ether 193 by using ( ] -allyl-PdCl)2 and chiral Trost L-2. Subsequent Heck reaction of 194 afforded 195 in 91 % yield when DPPP was used as a ligand. DPPF and DPPE gave lower yield [74]. [Pg.459]


Scheme 192. Reaction of Alkenyl Epoxides and Aziridines Producing Heterocycles via Carbon-Heteroatom Bond Formation by (a) Intramolecular Allylation of Oxygen and Nitrogen Nucleophiles and (b) Intermolecular [3 + 2]-Cycloaddition with Heterocumulenes... Scheme 192. Reaction of Alkenyl Epoxides and Aziridines Producing Heterocycles via Carbon-Heteroatom Bond Formation by (a) Intramolecular Allylation of Oxygen and Nitrogen Nucleophiles and (b) Intermolecular [3 + 2]-Cycloaddition with Heterocumulenes...

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Allylation nucleophiles

Allylation of Nucleophiles

Allylation of nucleophile

Allylic oxygenation

Nitrogen nucleophile

Nitrogen nucleophiles

Nitrogen oxygen and

Nucleophile oxygen

Nucleophilic oxygen

Nucleophilicity nitrogen nucleophiles

Oxygen nucleophiles

Oxygenated nucleophiles

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