Organolithium compounds with epoxides

FIGURE 9.66 Reaction of organolithium compounds with epoxides. 

The efficient synthesis of co-epoxide-ftmctionalized macromonomers in hydrocarbon solution at room temperature was achieved by optimizing the reaction of polymeric organolithium compounds with epichlorohydrin (eqn [28]). The direct addition of epichlorohydrin to a benzene solution of PSLi (Mn = 2000 g mol" ) formed the co-epoxide-frmctionalized polystyrene in only 9% yield the major products correspond to dimeric species (70%). Addition of THF to the solutions of PSLi and epichlorohydrin decreased the dimer yield to 10%... 

Benzyl methyl ether or allyl methyl ethers can be selectively metalated at the benzylic/allylic position by treatment with BuLi or sBuLi in THF at -40 °C to -80 C, and the resulting organolithium compounds react with primary and secondary alkyl halides, epoxides, aldehydes, or other electrophiles to yield the expected products [187, 252, 253]. With allyl ethers mixtures of a- and y-alkylated products can result [254], but transmetalation of the lithiated allyl ethers with indium yields y-metalated enol ethers, which are attacked by electrophiles at the a position (Scheme 5.29). Ethers with ft hydrogen usually undergo rapid elimination when treated with strong bases, and cannot be readily C-alkylated (last reaction, Scheme 5.29). Metalation of benzyl ethers at room temperature can also lead to metalation of the arene [255] (Section 5.3.11) or to Wittig rearrangement [256]. Epoxides have been lithiated and silylated by treatment with sBuLi at -90 °C in the presence of a diamine and a silyl chloride [257]. 

Epoxides can be reduced under Birch conditions by solvated electrons [34] and by arene radical anions [35] without the presence of low-valent metal complexes. In both cases )5-lithiumoxy organolithium compounds are formed after further reduction with a second equivalent of the electron transfer reagent. These species are stable enough to be trapped by electrophiles at low temperatures. They do not show the typical reactivity patterns of radicals. Thus, these transformations will not be dealt with here in detail. 

Likewise, the first step in the synthesis of 50 is a regioselective ring opening of epoxide 40 with organolithium compound 45. By a series of manipulations, sulfone 47c is produced in 50% overall yield with 97% ee [11]. Ring opening of lactone 48 with the lithiated sulfone 47c... 

There are limited data on 1,2-epoxy of glycal epoxide ring opening reaction with C-nucleophiles other than organocuprate, e.g., Grignard reagents [217, 218], organolithium compounds [217-219], aUylstannane [217], and sodio di-tert-butyl malonate [219, 220]. 

Bachki A, Foubelo F, Yus M (1996) Chiral Epoxides as a Source of Chiral (3-Oxido-Functionalized Organolithium Compounds Reaction with Electrophiles. Tetrahedron Asymm 7 2997... 

The simplest chain structure -f-CH2—S- occurs through the polymerization of thioformaldehyde, CH2S, or its cyclic trimer (trithiane). Aliphatic polysulfides with two or more carbon atoms per monomeric unit are available through the polymerization of cyclic sulfides. The start step with organolithium compounds deviates from that of the epoxides in that initially the sulfur atom is attacked and subsequently the carbon atom is attacked. For example, the starting step with propylene sulfide and ethyl lithium initially gives propylene and lithium ethane thiolate ... 

Grignard reagents and organolithium compounds react as carbon nucleophiles with a wide range of electrophilic functional groups, including epoxides (and many carbonyl-containing species discussed later in the book). 

Nonstabilized oxiranyl anions were generated by lithiation of terminal epoxides in the presence of a diamine ligand [35], this methodology being appUed to the asymmetric deprotonation of meso-epoxide 39 in the presence of (-)-sparteine. The resulting organolithium compound 40 reacted with different electrophiles to give compounds 41 in up to 86% ee (Scheme 2.6) [36]. 

Starting from different chiral epoxides, such as 255 or 256, and following the same protocol as for the epoxide 252, the expected primary organolithium intermediates 257 and 258 were generated, and then the final compounds 259 and 260, respectively, by reaction with different electrophiles and final hydrolysis in 69-80% and 70-90%, respectively. 

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