Alcohols heteroaryl substituted

The earliest oxidations were effected with nitrous fumes and later with mercuric oxide and isoamyl nitrite.74 Lead tetraacetate in acetic acid is in many cases the reagent of choice, but the removal of by-products can present some difficulties.75 IV-Haloimides and amides in alcoholic solutions have been reported to yield essentially pure tetrazolium salts76 and have been found specially useful in the preparation of heteroaryl-substituted tetrazolium salt.77,78 The novel formazans 49 have been successfully oxidized to 50 using 7V-chloro succinimide (Eq. II).79 tert-Butyl hypo-... 

In 2006, Birman and coworkers showed that dihydroimidazo[l,2-a]pyridine (DHIP) derivatives, such as CF3-PIP 20 and Cl-PIQ 22, as well as isothioureas such as benzotetramizole (BTM, 23) and HBTM (47) could serve as effective chiral catalysts for the acylative KR of racemic oxazoHdinones [123]. These catalysts, which rely on 7t-7T and cation-Ti interactions and which had already been successfully used in the enantioselechve acylation of benzylic alcohols, showed impressive selectivities in the case of 4-aryl- and 4-heteroaryl-substituted 2-oxazolidinones (Figure 41.12). 

Recently, many efforts have been focused on the development of the enantioselective (iodomethyl)zinc-mediated cyclopropanation of allylic alcohols. Kobayashi and co-workers reported that moderate to good enantioselectivities were observed if a Ci-symmetric chiral disulfonamide was added. " To reduce the rate of uncatalyzed process responsible for decrease of enantioselectivity, Charette and Brochu studied the effect of addition of Lewis acid, and proved that TiCU accelerates the reaction. The addition of the chiral titanium catalyst 548 allowed the conversion of 3-aryl and 3-heteroaryl-substituted allylic alcohols to the corresponding cyclopropane derivatives in enantiomeric ratios up to 97 3 (Scheme 2-154, eq. (a)). The dioxaborolane ligand 549 is an efficient chiral reagent for the enantioselective cyclopropanation not only of allylic alcohols but also of unconjugated and conjugated... 

A facile preparation of aryl or heteroaryl substituted methylphosphonate esters (470) in good yields, involving a Lewis acid mediated Michaelis-Arbuzov reaction of arylmethyl halides/alcohols (468) with triethyl phosphite (469) at room temperature, has been described by Mohanakrishnan et al. (Scheme 116). ... 

Thiazoles with Heterocyouc Substituents. Thiazoles with heterocyclic substituents in the 2- or 4-position have been synthesized (Table II-9). Thus thioacetamide (or its a-substituted derivatives) react with bromomethyl heteroarylketones under reflux in alcohol to give the corresponding 2-methyl-4-heteroarylthiazoles heteroaryl groups in the 4-position were 2 -thienyl (213, 692) a-pyrrolyl and 3-method derivatives... 

Aryl- and heteroaryl halides can undergo thermal or transition metal catalyzed substitution reactions with amines. These reactions proceed on insoluble supports under conditions similar to those used in solution. Not only halides, but also thiolates [76], nitro groups [76], sulfinates [77,78], and alcoholates [79] can serve as leaving groups for aromatic nucleophilic substitution. 

The majority of reported reactions of aryl and heteroaryl substrates with organocopper reagents are examples of Stephens-Castro coupling or the more recent catalytic version of that reaction. The reaction has found recent application in syntheses of C-(6)-substituted pterins and pteridines, substituted pyridines, and the antitumor antibiotic fredericamycin A," to name a few. Aryl iodide can be che-mospecifically displaced in the presence of bromide," and 2,5-dibromopyridine is regioselectively substituted at the 2-position. Substitution of halobenzenes by propargyl alcohol, followed by oxidative cleavage, provides a convenient route to terminal arylalkynes. " Fused heterocycles are formed in reactions of aryl halides bearing nucleophilic ortho substituents. - "... 

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