Ethers benzyl thioethers

Solutions of these metals in liquid ammonia effect (i) the reduction of a range of functional groups such as carbonyl and acetylenic and also conjugated and aromatic systems, and (ii) cleavage of benzyl and allyl ethers and thioethers. These reactions are usually carried out by the general procedure of adding the metal to a solution of the substrate in liquid ammonia to which dry methanol or ethanol or t-butanol has been added to provide a ready proton source (alcohols are more acidic than ammonia).34... 

Reactions of allyl and benzyl ethers and thioethers with magnesium... 

The position of the heteroatom may also strongly affect the global reactivity of the molecule. Thus, ethers, esters, thioethers, and even amines, that are normally weakly reactive toward the electron, can afford cleavage at the condition to be in an activated position (benzylic or allylic) to the X group (a fast cleavage of the radical anion results in a large shift to less cathodic potentials when the global bielectronic step is considered). In a different way, the reduction of ethers and amines could be achieved only under the conditions of the Birch reaction (i.e. reduction by Li metal in amines or by a solvated electron). These conditions can be electrochemically... 

Phase transfer reaction of the conjugate base of the JV,iV,iV -trialkylsulphamides (345) in the presence of benzyl triethylammonium chloride with chloromethyl ethyl ether or chloromethyl alkylthioethers yields the N,iV-dialkyl-iV -alkyl-iV -ether and thioether sulphamides (341)365 (equation 117). 

With Fe2(CO)9 as catalyst, the CDC reaction of saturated heterocycles with 1,3-diketones was accomplished using TBP as an eflhcient oxidant (Scheme 2.12) [48]. This protocol shows good compatibility to cyclic and acyclic ethers, thioe-thers, and tertiary amines. Gratifyingly, besides C(sp )-C(sp ) coupling, the oxidative C-N coupling of ethers with azoles also works well (Scheme 2.12) [49]. As a update, with 2-chloranil (tetrachloro-l,2-benzoquinone) as oxidant, benzyl thioethers can be employed as substrates under metal-free conditions [50]. Notably, 2,2,6,6-tetramethylpiperidine-l-oxoammonium tetrafluoro borate is also an effective oxidant for metal-free CDC reaction of isochromanes and carbonyl compounds [51, 52]. 

The treatment of 2-fluorophenyl-2-iodophenyl ethers, amines, and thioethers with 3.3 equivalents of f-BuLi and further reaction with selected electrophiles gave rise to functionalized carbazoles, dibenzofurans, and dibenzothiophenes in a direct and regioselective manner. A selected example is illustrated below <06JOC6291>. Benzyl 2-halophenyl ethers was treated with f-BuLi, and then reacted with carboxylic esters to give 2,3-disubstituted benzo[t>]furans <06JOC4024>. 

The reactivity of a series of thioethers has also been examined. It was found that the enantioselectivity is a function of the thioether alkyl group. The highest ee values were obtained with methyl and benzyl groups. Interestingly, X-ray analysis revealed that the stereochemistry of the reaction was the opposite of that obtained with analogous ether complexes (Scheme 49)90. 

A method has been described for the functionalization of the isopropylidene terminus of isoprenoids. For example, geranyl benzyl ether (208) was converted into the phenyl thioether (210) by treatment with PhSCl and elimination of HCl. Oxidation and reaction with trimethyl phosphite gave the primary alcohol (209) stereospecifically in 75% overall yield. Use has been made of this procedure in the synthesis of solanesol (C45) from three C15 units.The tosyl derivative of the hydroxylated farnesol (211) reacts with the bromide (212) prepared from (213) to give the C30 product (215), the bromide (216) of which, after further reaction with (214), affords the solanesol derivative (217) and thence solanesol (205). 

Removal of an electron generally brings about significant thermochemical C-H bond weakening both in a + n) radical cations (i.e. deprotonation in the benzylic position [152]) and a- -n) radical cations (i.e. deprotonation at the a-carbon of amines [153, 154], ethers [155], and thioethers [156]). The kinetic acidity of benzyl radical cations is rather well understood [152d, 157, 158], although occasionally an addition-elimination route was favored over direct proton transfer [159]. For alkyl arene radical cations [160] a linear relationship has been established between logkdep and thermochemical acidity [157]. 

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