Lithium cyclohexenolate

Tricyclic heptanones.1 The reaction of 1 with CHjMgBr and then with lithium cyclohexenolate results in 2 and the tricyclic product 3. The minor product 2 can be converted into 3 in high yield by further reaction with CH3MgBr and lithium... 

In the presence of HMPA, 1 1 dimers were observed with both lithium cyclohexenolate or 2,4-dimethylpentanolate and [6Li,15N]LDA or [6Li,15N]LiTMP297. The /S-aminoester enolate presented above (Scheme 60B) was also shown to provide a 1 1 mixed aggregate with LiHMDS in THF288. 

The catalytic system has been successfully extended to polymer-bound lithium amide co-bases of type 65 (see Table 4) which, like C—Li bases of type 63 and 64, are efficient regenerating agents of HCLA and poorly reactive toward oxiranes. For instance, the isomerization of cyclohexene oxide by 0.05 equiv of HCLA 55 in the presence of 1.45 equiv of 65 affords ( l-cyclohexenol in 92% ee (entry 15). It is of interest to note that, similarly to co-bases 63 and 64, the use of 65 leads to an increase of selectivity compared to the stoichiometric reaction at room temperature (Table 2, entry. ... 

Lithium amide deprotonation of epoxides is a convenient method for the preparation of allylic alcohols. Since the first deprotonation of an epoxide by a lithium amide performed by Cope and coworkers in 19585, this area has received much attention. The first asymmetric deprotonation was demonstrated by Whitesell and Felman in 19806. They enantioselectively rearranged me.vo-cpoxidcs to allylic alcohols for example, cyclohexene oxide 1 was reacted with chiral bases, e.g. (S,S) 3, in refluxing TFIF to yield optically active (/ )-2-cyclohexenol ((/ )-2) in 36% ee (Scheme 1). 

A few years later, Asami introduced the proline-derived chiral lithium amide 4 which proved to be more successful, producing (.S )-2-cyclohexenol ((. >)-2) with 80% ee (Scheme 2) 1. 

Vinyl sulfones are useful building blocks for synthetic organic chemistry. Nucleophilic epoxida-tion of chiral (,S )-2-tosyl-2-cyclohexenol (1) and its 0-protected derivatives proceeds with excellent diastcrcosclcctivitics and good yields.. mt-Epoxides 2 of 98% optical purity are obtained, except for the silylated derivative which is much less selective when epoxidized with lithium tt-77-butylperoxide, and, similarly to the acetyl derivative, is incompatible with standard Weitz-Scheffer conditions68. 

The most general synthetic route to benzene oxides-oxepins is that initially developed by Vogel for 1. 1,4-cyclohexadienes (readily available from [2+4] cycloaddition of alkynes and butadienes, lithium-ammonia reduction of arenes, or dehydration of cyclohexenols) were converted to dibromoepoxides, the immediate precursors of benzene oxides. Modifications of this route have been used to prepare Ic and Id. Treatment of the monosubstituted arene oxide 43 (Figure 3) with (Et)4NF or thermal isomerization of 3-oxaquadricyclane provide additional synthetic routes to la. Similarly, the thermal (or photochemical) isomerization of the monoepoxide of Dewar benzene yielded la. ... 

In Chapter 19 (Section 19.2), lithium aluminum hydride and sodium borohydride reacted with ketones or aldehydes via acyl addition to reduce the carbonyl to the corresponding alcohol. This reaction is complicated by the presence of a conjugating n-bond. When cyclohexenone reacts with LiAlH4, the product is a mixture of cyclohexenol (66) and cyclohexanol (67). Cyclohexenol results from 1,2 addition of the hydride, but 67 results from 1,4 addition and 1,2 addition. 

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