Bis allylic alcohol

Desymmetrization of meso-bis-allylic alcohols is an effective method for the preparation of chiral functionalized intermediates from meso-substrates. Schreiber et al has shown that divinyl carbonyl 58 is epoxidized in good enantioselectivity. However, because the product epoxy alcohols 59 and 60 also contain a reactive allylic alcohol that are diastereomeric in nature, a second epoxidation would occur at different rates and thus affect the observed ee for the first AE reaction and the overall de. Indeed, the major diastereomeric product epoxide 59 resulting from the first AE is less reactive in the second epoxidation. Thus, high de is easily obtainable since the second epoxidation removes the minor diastereomer. 

First, in a Grignard reaction, vinyl magnesium bromide is added to the dialdehyde 29 to give the corresponding bis-allyl alcohol, which is oxidized in the second step to form the a,P-unsaturated diketone 30 using Dess-Martin periodinane. 

Tertiary bis(allylic) alcohols are oxidized by PCC or PDC to the carbonyl transposed dienones. ... 

The enantioselective total synthesis of the annonacenous acetogenin (+)-parviflorin was accomplished by T.R. Hoye and co-workers." The b/s-tetrahydrofuran backbone of the natural product was constructed using a sequential double Sharpless asymmetric epoxidation and Sharpless asymmetric dihydroxylation. The bis allylic alcohol was epoxidized using L-(+)-DET to give the essentially enantiopure bis epoxide in 87% yield. 

Epoxidation of the C2-bis allylic alcohol also provides the diepoxide 16 in high enantiomeric excess (>97% ee [53].)... 

In 1991, Hoye was the first to report the total synthesis of an acetogenin /rexepr -uvaricin 90, which has in common with natural uvaricin the right relative configuration across the THF skeleton but is of the opposite absolute configuration (2). The strategy used as a key step the asymmetric epoxidation of a homochiral bis-allylic alcohol, which allowed 5 out of 6 stereocentres to be built up at once with the desired relative configuration. A few more steps were necessary for the inversion of the last stereocenter (Fig. 10). 

The bis(tetrahydrofuranyl) Annonaceous acetogenin ( + )-(15,16,19,20,23,24)-hexepiuva-ricin (74), has been synthesized utilizing a polyepoxide cascade reaction. The diiodide 70 is transformed into the bis-allylic alcohol 72, which is subsequently converted to a C2-sym-metric diepoxide utilizing the Sharpless asymmetric epoxidation reaction. Selective mono-tosylation of the primary hydroxyl groups served to desymmetrize the system. An acid-catalyzed deketalization followed by simultaneous epoxide opening affords the erythro trans threo trans erythro-conf gmdXion present in the tosylate 73. Transformation of 73 to the desired 74 completes the synthesis [32] (Scheme 17). 

If the epoxidation reaction is carried out with enantiomerically pure secondary allylic alcohol, then high yields of the desired epoxide can be obtained. Selective epoxidation of a single enantiomer of the bis-allylic alcohol 56 with (+)-DIPT gave the mono-epoxide anti-tumor agent laulimalide 57 No epoxidation of the... 

Nelson has recently introduced an example of the Ir(I)-catalyzed olefin isomerisation followed by the Claisen rearrangement for the conversion of bis-allylic alcohol 39 to aldehyde 40. ... 

W. S. Johnson and coworkers developed this protocol in the course of endeavours towards the synthesis of all /ra 5 -squalene. Upon heating with ethyl orthoacetate, the bis-allylic alcohol 342 yielded di-ester 343 to accomplish a double homologation strategy. Johnson recognized the potential of this [3,3]-sigmatropic rearrangement since the operation simultaneously produced two -trisubstituted alkenes as a single diastereomer. Further elaboration of intermediate 343 resulted all ( )-squalene. 

Interestingly, attempts to use the bis-allylic alcohol as the substrate in the analogous reaction led to isolation of the ferrilactone complex (61) as the major product, accompanied by a trace of the trimethylenemethane complex. Conversely, reaction in THF at room temperature resulted in a complete reversal of the product distribution [256] (Scheme 136). The reasons for this are currently unclear. 

This methodology has been applied to the construction of a variety of stereoisomers of polypropionate skeletons, as exemplified by the formation of a tetraol from a symmetrical bis-allyl alcohol by a sequence involving three intramolecular hydrosilation-oxidation steps (eq 3). ... 

---