Olefin structures reduction

Hydroboration of conjugated systems has not been studied extensively. However, the apparent 1,4-reduction [3 ] of the 5,7 diene system (3) (see Fig. 25) occurs by the formation of the 5a-H, 6a-borane, A -olefin structure (4) which on subsequent treatment with acid loses its boron content with rearrangement to give the 6,7-olefin (5) [38]. 

The observations (29) on the homogeneous reduction of coordinated olefins confirms the possibility of mechanism (1). It seems unlikely that TT-allyl-adsorbed olefin [Structure (C)] will pass directly into an alkyl radical without either (A) or (B) intervening as in mechanism (1) or (2), although the process... 

Branching of the olefin structure always decreases the reaction rate. The strongest decrease occurs when one of the carbon atoms of the double bond is substituted. Branching at more distant carbons gives a less marked, but still significant reduction in reactivity. The slowest rates occur with internal, double bond substituted olefins. 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

The stereochemical course of reduction of imonium salts by Grignard reagents was found to depend on the structure of the reagent 714). Hydro-boration of enamines and oxidation with hydrogen peroxide led to amino-alcohols (7/5). While aluminum hydrogen dichloride reacted with enamines to yield mostly saturated amines and some olefins on hydrolysis, aluminum hydride gave predominantly the unsaturated products 716). 

If saturation occurs first, the product will be relatively stable toward further reduction but if hydrogenolysis occurs first, the resulting olefin is readily reduced. This ratio depends greatly on substrate structure, the catalyst, and environment. Hydrogenolysis is best achieved over platinum, whereas palladium (77a,82a,122bJ62a), rhodium (I09a), or ruthenium (I0a,I09a) tend to favor olefin saturation. 

The numerous biotransformations catalyzed by cytochrome P450 enzymes include aromatic and aliphatic hydroxylations, epoxidations of olefinic and aromatic structures, oxidations and oxidative dealkylations of heteroatoms and as well as some reductive reactions. Cytochromes P450 of higher animals may be classified into two broad categories depending on whether their substrates are primarily endogenous or xenobiotic substances. Thus, CYP enzymes of families 1-3 catalyze... 

The reaction of methyl acrylate and acrylonitrile with pentacarbonyl[(iV,iV -di-methylamino)methylene] chromium generates trisubstituted cyclopentanes through a formal [2S+2S+1C] cycloaddition reaction, where two molecules of the olefin and one molecule of the carbene complex have been incorporated into the structure of the cyclopentane [17b] (Scheme 73). The mechanism of this reaction implies a double insertion of two molecules of the olefin into the carbene complex followed by a reductive elimination. 

A wide variety of activated olefins (126) undergo reductive electrochemical dimerization to compounds of structure 127 (electrolytic hydrodimerization) 129 i. While the product 127 is capable of existing in either dl or meso modifications, relatively little attention has been paid to the stereochemistry of hydrodimers... 

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