Inside oxygen effect

The oxygen atom has also been used to generate other functionalities, such as the aldehyde moiety in Kibayashi s syntheses of (—)-coniine (197) and its enantiomer (Scheme 1.43) (253). Here, reaction of tetrahydropyridine N-oxide 93 with a silylated chiral allyl ether dipolarophile 198 delivered the adduct 199 with the desired bridgehead stereochemistry via the inside alkoxy effect . Desilylation and hydrogenolytic N—O bond rupture with palladium(II) chloride provided the diol 200... 

In contrast to the dihydroxylations, the hydroboration of allylic alcohols takes place without an inside alkoxy effect in the sense 5.132 with the oxygen atom treated as the medium-sized group. It is probably significant that the inside alkoxy effect is most noticeable with reagents which are relatively electrophilic in nature, and not with boranes, which are only mildly electrophilic. 

The inside alkoxy effect is useful for predicting the stereoselectivity of nitrile oxide cycloaddition reactions with chiral lylic ethers. The hypothesis states that allylic ethers adopt the inside position and alkyl substituents prefer the sterically less-crowded anti conformation in transition states for these electrophilic cycloadditions . The terms inside and outside are defined in (17) for a hypothetical nitrile oxide cycloaddition transition state. Both ab initio (Gaussian 80 with 3-2IG basis set) and molecular mechanics calculations agree, each predicting the lowest-energy transition state to be the one described, i.e. (18 H outside) just above it lies one where the alkyl group is anti, OR outside and H inside (19 ). As illustrated, the former leads to a product wherein OR and the nitrile oxide oxygen are anti, the latter to one with them syn (Scheme 19). 

The influence of pH on the affinity of Hb for oxygen known as the Bohr-effect indicates that protons retain the allosteric regulation of oxygen transport. It is also an indirect confirmation of the ability of Hb and Im Hb for transporting carbon dioxide. The values of the Bohr-effect d log P50/d pH for Hb and Im Hb are close to each other in the pH range 7.1-7.4. It is possible that the effect of the micro-environment of carboxylic CP on immobilized Hb and its polyfunctional interaction represents the interaction between Hb and the structural elements inside the red cell [99]. 

Kabbabi A, Gloaguen F, Andolfatto F, Durand R. 1994. Particle-size effect for oxygen reduction and methanol oxidation on Pt/C inside a proton-exchange membrane. J Electroanal Chem 373 251-254. 

The rationalization of stereoselectivity is based on two assumptions. (1) The 1-arylthio-1-nitroalkenes adopt a reactive conformation in which the ally lie hydrogen occupies the inside position, minimizing 1,3-allylic strain. (2) The epoxidation reagent can then either coordinate to the ally lie oxygen (in the case of Li), which results in preferential syn epoxidation or in the absence of appropriate cation capable of strong coordination (in the case of K) steric and electronic effects play a large part, which results in preferential anti epoxidation (Scheme 4.7).52... 

Figure 3.7 An anti-smoking device the cigarette is inserted into the wider end. Partially oxidized carbon monoxide combines chemically with oxygen inside the device after leaving the end of the cigarette but before entering the smoker s mouth the oxygen necessary to effect this oxidation enters the device through the small circular holes positioned along its length...

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