Lithium tetramethylpiperidide, epoxide

Terminal epoxides 140 are deprotonated at 0°C using lithium tetramethylpiperidide (LiTMP). The resulting anion reacts with alkyl- and alkenylmagesium reagents under ring-opening. LiiO is eliminated and alkenes 141 are formed (equation 76) . ... 

Eliminations of epoxides lead to allyl alcohols. For this reaction to take place, the strongly basic bulky lithium dialkylamides LDA (lithium diisopropylamide), LTMP (lithium tetramethylpiperidide) or LiHMDS (lithium hexamethyldisilazide) shown in Figure 4.18 are used. As for the amidine bases shown in Figure 4.17, the hulkiness of these amides guarantees that they are nonnucleophilic. They react, for example, with epoxides in chemoselective E2 reactions even when the epoxide contains a primary C atom that easily reacts with nucleophiles (see, e.g., Figure 4.18). 

In an unusual example of the epoxide moiety acting as a nucleophile, Hodgson and co-workers <02TL7895> have reported on a convenient method of deprotonating terminal oxiranes with lithium 2,2,6,6-tetramethylpiperidide (LTMP), followed by trapping of the anion with silyl-based electrophiles, to provide a,p-epoxysilanes in good yield. For example, chloro-epoxide 56 underwent clean conversion to epoxysilane 57 at 0 °C. This approach improves upon an earlier method, which employed sparteine derivatives at very low temperature (-90 °C) <01OL461>. 

Vinyl epoxides can also be ring-opened via an Sn2 sense, as exemplified in the macrocyclization of the epoxy-tethered cyclopentenone 76, which was induced to occur by treatment with lithium 2,2,6,6-tetramethylpiperidide (LTMP) followed by the mild Lewis acid diethylaluminum chloride in THF. The enolate attacked exclusively from the a-position of the... 

Nozaki and Yamamoto reported a novel method for regiospecific isomerization of epoxides to allylic alcohols based on diethylaluminum 2,2,6,6-tetramethylpiperidide (DATMP) which can be prepared in situ from Et2AlCl and lithium 2,2,6,6-tetramethylpiperidide (LiTMP) (molar ratio 1 1) in benzene at 0 °C for 30 min [119], Reaction of DATMP (4 equiv.) with ( )-cyclododecene oxide in benzene at 0 °C for 3 h produced ( )-2-cyclododecen-l-ol in 90 % yield. Interestingly, the reaction of diepoxide 121, a useful synthetic intermediate in the preparation of Cig-Cecropia juvenile hormone, with DATMP furnished the triol 122 in 41 % yield (Sch. 83). 

This was the first-described, non-stabihzed ylide, obtained by treatment of the corresponding telluronium tetrafluoroborate with lithium 2,2,6,6-tetramethylpiperidide (LiTMP). Epoxides are obtained by reaction with both aldehydes and ketones. ... 

A hindered Hthium amide such as lithium 2,2,6,6-tetramethylpiperidide (LTMP) has proved to be effective in triggering a direct intramolecular cyclopropanation of the unsaturated terminal epoxide 31 to the tricycHc alcohol 32 (2010JOC2157). This strategy has been used successfully in a concise synthesis of (—)-cubelol (33) from (—)-menthone. Similarly, the naturally occurring (—)-10-epicubelol (34) can be prepared from (+)-menthone. Interestingly, whatever is the stereochemistry of the tethered alkene, the facial selectivity of cyclopropanation is controlled solely by the epoxide stereochemistry (Scheme 8). 

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