Allylic alcohols acyclic derivatives

Stereoselective cyclopropanation of acyclic allylic alcohols glucose-derived chiral auxiliary24 1... 

An allylic sulfenate, like 199, is known to be in equilibrium with allylic sulfoxide, like 196, although its concentration is usually low . Various allylic sulfoxides can be prepared by treatment of allylic alcohols with arenesulfenyl chlorides . Evans and coworkers prepared various allylic alcohols by treating the corresponding allylic sulfoxides with trimethyl phosphite. For example, the carbanion from a cycloalkenyl sulfoxide 201 was readily alkylated at the a-position by treatment with alkyl halide. The resulting alkylated derivative 202 was then treated with trimethyl phosphite and 3-substituted cycloalkenol was obtained. Alkylation of acyclic allylic sulfoxide 204 gave... 

One of the classical ways to perform diastereoselective 1,3-dipolar cycloaddition is by the addition of a 1,3-dipole to an allyl alcohol derivative (65, 107-120). Very recently, a short review article was devoted to this area (13). Among the most commonly applied acyclic allyl alcohol derivatives are alkenes 73-75 (Scheme 12.25). These alkenes have been used in reactions with nitrones. 

Cyclizations of chloral hemiacetal derivatives of cyclic allyl alcohols were regio- and stereo-selective (Table 6, entry 1), but a mixture of regioisomers was obtained from analogous derivatives of acyclic allyl alcohols with a nonterminal double bond.93 Hemiacetal derivatives of allyl alcohols with a terminal vinyl group have been cyclized with mercury(II) acetate to give acetal derivatives of threo 1,2-diols with moderate selectivities (equation 54 and Table 15, entries 1 and 2).147 Moderate to excellent stereoselectivity has been observed in the iodocyclizations of carbonate derivatives of allyl alcohols (entries 3-5).94a The currently available results do not provide a rationale for the variation in observed stereoselectivity. 

Table 15 O-Cyclizations of Derivatives of Acyclic Allylic Alcohols (Equation 54)...

Hydroboration of alkenes1 (15, 91). The Rh(I)-catalyzed hydroboration provides a highly diastereoselective reaction in a synthesis of a poly ether antibiotic. Thus the derivative (1) of an acyclic allylic alcohol is converted to the primary alcohol 2 by hydroboration with catecholborane (CB) catalyzed by ClRh[P(C6H5)3]3 with 94 6 selectivity. Note that hydroboration of 1 with disiamylborane (12, 484) proceeds with the opposite selectivity at Cio (8 92). 

A CM reaction of the allylic alcohol derivative 130 and the enone 131 provided the acyclic precursor 132 for the synthesis of (+)-carpamic acid 133 <04TL1167>. 

Chamberlin AR, Dezube M, Dussault P, McMills MC (1983) Iodocyclization of allylic alcohol derivatives containing internal nucleophiles. Control of stereoselectivity by substituents in the acyclic precursors. J Am Chem Soc 105 5819-5825... 

Located at an "ofif-template" site, we expected the Cl 4 center to be more difficxilt to establish and verify. We were going to have to rely on precedents of acyclic stereoselection, and based on Kishi s empirical observations (ref. 30), hydroxylation of olefin 32b should have given the R epimer 33, preferentially. On the other hand. Cram chelate addition (ref. 31), as elaborated by Still (ref. 32), to the a-benzyloxy ketone 32a, should give the allyl alcohol 34 from which the S-epimer 35 could be derived. Indeed, both processes were entirely stereoselective, and we were able to prepare the two possible products, each as a single isomer. 

Most allylic substitution reactions have been conducted witti derivatives of allylic alcohols, such as acetates, phosphates, and carbonates. These reactions occur with allyl electrophiles displaying a wide structural variation. The allylic electrophiles can be cyclic or acyclic, substituted with aliphatic or aromatic groups, substituted at one or both termini, and substituted or unsubstituted at the central carbon. As discussed in more detail below, these substituents affect the regioselectivity of the substitution process. 

FIGURE 7.16 Intramolecular acyclic terpene derivatives isommzation through the formation of allyUc cationic species and the effect of the resorcin[4]arene capsule on the product distribution of the reaction for (a) allyl alcohols and corresponding (b) acetate esters as substrates. (Adaptedfrom Ref. [66] with permission of Nature Publishing.)... 

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