Remote group interaction

Compounds 45 exhibit, in addition to sulfone-sulfmate rearrangements1 2 4-6 11, alkyl sulfone cleavages4,6,27, intramolecular Smiles-type rearrangements33 and extrusion of S023,5,29,30, an exceptional mode of remote group interaction which leads to the loss of... 

If the rotational freedom of the aryloxy group is restricted, as in 4-[(arylsulfonyl)methyl]-2H-l-benzopyranes (55), the remote group interaction is not possible anymore and these derivatives fragment mainly by ejecting ArS02H and S0238 (equation 26). 

The asymmetric induction cannot be explained simply by steric interaction because the R group in the aldehyde is far too remote to interact with the tartrate ester. In addition, the alkyl group present in the tartrate ligand seems to have a relatively minor effect on the overall stereoselectivity. It has thus been proposed that stereoelectronic interaction may play an important role. A more likely explanation is that transition state A is favored over transition state B, in which an n n electronic repulsion involving the aldehyde oxygen atom and the /Mace ester group causes destabilization (Fig. 3-6). This description can help explain the stereo-outcome of this type of allylation reaction. 

Dibenzoates of chiral diols exhibit two c.d. maxima, of similar intensity but opposite sign, in the regions of 219 and 233 nm, respectively, due to the dipole-dipole interaction between the two ester groups. The shape of the resulting curve indicates the chirality of the diol (Figure 4), and is not limited to vic-diols e.g. 2,3- or 3,4-diols), but applies also to more remote groups (e.g. a 3/S,6)S-diol). 

Early results with these systems were encouraging. A comparison of 2-(I) and 4-(methoxyphenoxy)methyl (II) (CH3-0-C6H4-0-CH2-) derivatives of 15-crown-5 (III) with the latter compound proved instructive. Liotta (8) reported that the cyclization yield for 15-crown-5 was 29%. We found that when the methoxy group was para and too remote to interact with a ring-bound cation, the cyclization yield was 30%. When the methoxy group was ortho, the cyclization yield more than doubled (ca. 70%). Two-phase extraction constant studies (9) also proved encouraging. The method involves extraction of sodium picrate from water into a nonpolar solvent like chloroform or dichloromethane. The picrate anion is highly colored and its... 

We can divide commodity plastics into two classes excellent and moderate insulators. Polymers that have negligible polar character, typically those containing only carbon-carbon and carbon-hydrogen bonds, fall into the first class. This group includes polyethylene, polypropylene, and polystyrene. Polymers made from polar monomers are typically modest insulators, due to the interaction of their dipoles with electrical fields. We can further divide moderate insulators into those that have dipoles that involve backbone atoms, such as polyvinyl chloride and polyamides, and those with polar bonds remote from the backbone, such as poly(methyl methacrylate) and poly(vinyl acetate). Dipoles involving backbone atoms are less susceptible to alignment with an electrical field than those remote from the backbone. 

This style of collaboration is common when each participant is one role of many played by some other object and the collaboration is part of a framework. These generic pieces of design are rarely about one object. Instead, they are about the relationships and interactions between members of groups of objects. Most of the design patterns discussed in books and bulletin boards are based on such collaborations for example, the observer pattern, which keeps many views up-to-date with one subject or proxy, which provides a local representative of a remote object or any of the more specialized design ideas that are fitted together to make any system. 

Methyl isobutyl ketone was reduced with (- )-menthol-LAH in ether to give the (+ )-(S)-carbinol (53) in low optical yield. Methyl neopentyl ketone was similarly reduced to the (-I- )-carbinol, although pinacolone was reduced to only racemic alcohol. Maximum stereoselectivity in the reduction of both ketones and alkenynols was obtained with a 2 1 (-)-menthol-LAH reagent. The observed low stereoselectivity was attributed mainly to insufficient interaction of the remote isopropyl substituent on the menthyl group with the substituents on... 

Parsley, spinach, French bean, poplar and S. obliquus (but not A. variabilis) conform extensively to the above criteria for reaction at the remote site. There is extensive evidence for cytochrome f reacting at the remote site on plastocyanin. The aromatic residue at 83 would seem to be a prime candidate as lead-in group for electron transfer. Desolvation at the surface around 83, and interaction with an aromatic component on the reaction partner, e.g. the porphyrin ring of cytochrome f, may be important. The exact manner of electron transfer has yet to be confirmed. The distance from the aromatic ring of Tyr83 to the Cu for electron transfer is 12 A. 

The high electrophilicity of the positively charged element can be modified by intramolecular donation from remote donor substituents. This interaction leads to solvent-free cations with coordination numbers for the positively charged element > 3 and to a considerable electron transfer from the donor group to the element. Frequently used donor substituents utilize heteroatoms with lone pairs (e.g. amino, hydrazino, methoxy, carboxy, phosphino, etc.), in many cases in combination with pincer-type topology of the ligand, for the stabilization of the cationic center. These strongly stabilized cations are beyond the scope of this review and instead we will concentrate on few examples where we have weak donors such as CC multiple bonds, which stabilize the electron-deficient element atom. 

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