Regiospecific substrate oxidation

For the prediction of regiospecific substrate oxidation, QM calculations and MD simulations have been combined to account for differences in reactivity in the substrate as well as distributions of multiple binding conformations, as applied for CYPs 101 (cam) (111,115,116), 107A (EryF) (117), and 2E1 (82). For CYP102 (BM3), probabilities for substrate orientation based on statistics of substrate binding from MD simulations were combined with probabilities for substrate reaction based on QM calculations of H-atom abstraction by a hydroxyl radical (89). The experimentally known preference for subterminal, distal hydroxylation of octane, octanoic acid, and lauric acid are thus reproduced. 

The Tsuji-Trost reaction is the palladium-catalyzed allylation of nucleophiles [110-113]. In an application to the formation of an A-glycosidic bond, the reaction of 2,3-unsaturated hexopyranoside 97 and imidazole afforded A-glycopyranoside 99 regiospecifically at the anomeric center with retention of configuration [114], Therefore, the oxidative addition of allylic substrate 97 to Pd(0) forms the rc-allyl complex 98 with inversion of configuration, then nucleophilic attack by imidazole proceeds with a second inversion of configuration to give 99. 

Cycloaddition between electron rich 6-[(dimethylamino)methylene]amino-l,3-dimethyl uracil and various electron deficient substrates gave pyrido[2,3-i pyrimidine derivatives in a high regiospecific manner. The pyrido[2,3-i pyrimidinones 17 and their N-oxides 18, 5-deaza-5,8-dihydropterins 19 and pyrido[2,3-i (]pyrimidinone 20 were synthesized from 6-aminouracils, 6-hydroxyaminouracils, 2,6-diaminopyrimidin-4-one and 6-amino-l,3-dimethyl-5-formyluracil, respectively " . ... 

It has been established that thiophenes undergo regiospecific oxidative cyanation at C-2 with TMSCN, as illustrated by the general transformation of 41 into 42 <05OL537>. Conversion of 3-bromobenzo[6]thiophene to benzo[6]thiophene-3-carbonitrile has been accomplished by treatment of the substrate with Zn(CN)2 in the presence of a catalytic system consisting of Pd/C, Zn dust, Br2, and PPhs in A/jA -dimetliylacetamide <05TL 1849>. 

Cycloaddition between electron-rich 6-[(dimethylamino)methylene]amino-1,3-dimethyl uracil 242 and various electron-deficient substrates such as quinones 243 and coumarins 244 was considered to take place by elimination of dimethyla-mine from the respective cycloadducts, followed by oxidative aromatization in a highly regiospecific manner to give pyrido[2,3-solvent-free conditions, the times were reduced to 6-7 min and the yields were increased from 70-80% to 85-94% (04SL1179). 

The regiospecificity of cyclohexadienyl complex formation via the oxidation of [Fe(CO)3 77" -substituted diene)] substrates by thallium tris(trifluoroacetate) has been examined.These reactions are considered to proceed via initial electrophilic attack of Tl(III) at the coordinated diene to give allyl intermediates such as (56) and (57). By using optically active starting diene complexes it was confirmed that... 

Treatment of the sulfenyl thiocarbonates formed from thiols and Scm-Cl with an equimolar amount of /7 chloroperbenzoic acid in chloroform generates the corresponding sulfinyl thiocarbonate which, unlike its precursor, is reactive towards ethanol in the presence of catalytic amount of imidazole. The latter reaction also establishes the regiospecificity of the oxidation reaction. The oxidation of the same sulfenyl thiocarbonate substrate with excess fflCPBA (min. 2.4 mol mCPBA/mol substrate) produces the corresponding sulfonyl thiocarbonate (eq 12). ... 

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