Acyclic epoxy alcohols

Walsh developed a highly enantio- and diastereoselective one-pot method for the efficient synthesis of acyclic epoxy alcohols and allylic epoxy alcohols [263]. This method took the advantage of a highly enantioselective C-C bond-forming reaction to set the initial chirality. The resulting allylic zinc alkoxide intermediate is then epoxidized in situ using either O2 or TBHP in the presence of a titanium... 

Epoxy alcohols. A few years ago Mihelich1 was granted a patent for preparation of epoxy alcohols by photooxygenation of alkenes in the presence of titanium or vanadium catalysts. Adam et al.2 have investigated this reaction in detail and find that Ti(IV) isopropoxide is the catalyst of choice for epoxidation of di-, tri-, and tetrasubstituted alkenes, acyclic and cyclic, to provide epoxy alcohols. When applied to allylic alcohols, the reaction can be diastereo- and enantioselective. The reaction actually proceeds in two steps an ene reaction to provide an allylic hydroperoxide followed by intramolecular transfer of oxygen catalyzed by Ti(0-i-Pr)4. The latter step is a form of Sharpless epoxidation and can be highly stereoselective. 

A wide variety of other alcohol substrates has been resolved, including aryl substituted secondary alcohols, - a-alkyl-P-hydroxy esters, P-hydroxy nitriles, and fluoroorganic compounds. Active chloroacetate esters are commonly used to speed up the hydrolysis reactions, as exemplified in eq 2 Primary acyclic alcohols possessing a stereogenic center that have been resolved include 2,3-epoxy alcohols, - 2-amino alcohols, and crown ethers. ... 

Vanadium catalysts have found particular advantage for stereoselective epoxi-dations. Thus, the acyclic allylic alcohol 34 is oxidized with high selectivity using t-BuOOH and vanadium acetylacetonate, whereas with mCPBA a nearly equal mixture of the diastereomeric epoxides was produced (5.45). 

With regard to synthetic applications, it is certainly important to mention that this substitution is not affected by the Cj-substituent and that it can be run with cyclic and acyclic cis-2,3-epoxy alcohols too. 

The same authors showed that this type of rearrangement is applicable to the case of acyclic 2,3-epoxy alcohols, such as (48), to give P-hydroxy ketone (49) (Equation 31) [32]. 

The kinetic resolution by etherification has also been conducted through the cyclization of epoxy aliphatic alcohols.274 In these reactions catalyzed by monomeric complex 51, the ring closure of acyclic substrates occurred with exclusive / -selectivity (Equation (74)), whereas m -openings were observed in the desymmetrization of... 

R2Cu(CN)Li2 reaction with vie-epoxy mesylatesA higher-order cuprate reacts selectively with the epoxide group of the epoxy mesylate 1 to provide 2 with inversion at C3. Ring closure of 2 furnishes the epoxide 3, which reacts with a second equivalent of the higher-order cuprate to furnish meso-4, with inversion at both C, and C3. This two-step reaction provides a route to acyclic alcohols with useful stereocontrol at both adjacent centers. 

Stereocontrolled epoxidation of acyclic systems. Stereoselectivity in the epoxi-dation of homoallylic alcohols is usually low. Nonetheless Kishi etal. have observed... 

There are a few applications of the Wharton reaction in acyclic systems. For example, treating an acyclic a, -epoxy ketone (Scheme 19) with hydrazine hydrate at 0 °C affords the expected product, but as a l l-( ) ( mixture. However, the major product (60%) in this particular case is the bicyclic alcohol that arises via cyclization of the intermediate vinyl radical (or anion) on the endocyclic carbon-carbon double bond. 

The mapping shown in Fig. 1 includes references to SBR and styrene block copolymers in the PB search. Removing these citations from the database reduced the number to 4297, which can be seen mapped in Fig. 3. the area of high activity is centered on hydroxy terminated PB (HTPB). Low-Mn HTPB can be prepared by a variety of polymerization processes such as radical, anionic, or even using acyclic diene metathesis (ADMET).f The HTPB has a variety of uses as a propellant. " Other uses include reaction with epoxy resins, nylon, urethane, or even in the formulation of adhesives.t" The use of HTPB as an oxygen scavenger in polyamide, polyvinyl alcohol, and multilayer... 

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