Ortho-substituted aromatic

This synthesis works especially well with cyclohexanone giving 80% oxaziridines with either chloramine (77JPR195) or (V-chloromethylamine. Simple aliphatic ketones and ortho substituted aromatic aldehydes yield 30-50% oxaziridines with N-chloromethylamine (65CB2516). 

Through the use of a tin(iv) enolate with benzaldehyde it was possible to generate the anti A diastereomer 47 with high selectivity (Entry 5). With tin(n) etiolates a highly substituent-dependent outcome was observed. Low selectivities resulted with para-substituted aromatic aldehydes, but good selectivities were observed for ortho-substituted aromatic aldehydes (Entries 7-9). Simultaneous re-... 

Other dialdehydes, keto aldehydes, hydroxyl aldehydes, ortho-substituted aromatic dialdehydes, and ortho-substituted aromatic hydroxyl aldehydes have been claimed to be active in a similar way [459]. 

In order to correlate rate constant data for aliphatic and ortho substituted aromatic compounds, one must allow not only for the polar... 

Taft steric Steric effects in aliphatic and ortho-substituted aromatic systems... 

High anti-diastereoselectivity is observed for several aromatic imines for ortho-substituted aromatic imines the two newly formed stereocenters are created with almost absolute stereocontrol. Aliphatic imines can also be used as substrates and the reaction is readily performed on the gram scale with as little as 0.25 mol% catalyst loading. Furthermore, the Mannich adducts are readily transformed to protected a-hydroxy-/8-amino acids in high yield. The absolute stereochemistry of the Mannich adducts revealed that Et2Zn-linked complex 3 affords Mannich and aldol adducts with the same absolute configuration (2 R). However, the diastereoselectiv-ity of the amino alcohol derivatives is anti, which is opposite to the syn-l,2-diol aldol products. Hence, the electrophiles approach the re face of the zinc enolate in the Mannich reactions and the si face in the aldol reactions. The anti selectivity is... 

The actual shape and size of the molecules depend on the substitution pattern of the arylene units. Although pure para-substituted cyclic phenylene-arylenes have been investigated, e.g. 1, most PAMs contain meta- or ortho-substituted aromatics at their corners and para-substituted aromatics for size expansion, respectively (2, Fig. 6.2) [11], The position where the side-groups are attached to the backbone determines if they point to the inside (intra-annular substituents, I, I ), to the outside (extra-annular substituents, E, E ) or if they can change their orientation according to an external parameter (adaptable substituents, A, A ). 

Another useful feature of the organopalladium reaction is that it can produce fairly hindered olefins from ortho-substituted aromatic mercurials. For example, "2,4,6-triisopropylphenylpalladium chloride , prepared in situ, from the mercurial and lithium chloropalladate in acetonitrile solution, reacts with styrene to produce a 40% yield of fra s-2,4,6-triisopropylstilbene. This is about the same yield of product that is obtained with the unsubstituted "phenylpalladium chloride under the same conditions 24>. 

Products of the Reaction. A solution containing 5 X 10"2 mole/liter hydroperoxide and 2 X 10"2 mole/liter dilauryl thiodipropionate was allowed to react at 70 °C. until no hydroperoxide remained. A brown resinous precipitate was formed which was filtered, washed, and dried in vacuo. The infrared spectrum of the solid revealed the presence of —O—SOo— groups and the presence of an ortho-substituted aromatic compound, but no further details of its constitution could be obtained. This precipitate was not formed in the kinetic experiments which had a... 

The mechanism proposed so far takes account of the induction period and initial stages of the reaction only, and it is difficult to see how it can account for the large amount of hydroperoxide decomposed by the sulfur compound. However, Tetralin hydroperoxide is decomposed catalytically by acids (5). Although in the absence of dilauryl thiodipropionate the decomposition of Tetralin hydroperoxide in the presence of acetic acid at 70 °C. was very slow, if the acid species is a much stronger acid than acetic—e.g., a sulfonic acid as seems likely from the nature of the products of the reaction, the rate of acid-induced decomposition may be comparable with the rate of decomposition by the sulfur compound. Some evidence that acid-induced decomposition does occur at some stage in the over-all reaction is found in the presence of an ortho substituted aromatic compound in the solid product of the reaction. The acid catalyzed decomposition of Tetralin hydroperoxide follows the path of Reaction 14 (5) to give y-(o-hydroxyphenyl)butyraldehyde. This forms a brown resin which is mainly the aldol of this aldehyde (cfthe resin obtained in this work). 

It was not a perfect correlation but Hammett had removed the examples where steric hindrance was important. Aliphatic compounds can adopt a variety of conformations (Chapter 18) and the substituent in some of them will interfere with the reaction. Similarly, in ortho-substituted aromatic compounds the nearby substituent might exert steric hindrance on the reaction. Only with meta-and para-substituted compounds was the substituent held out of the way, on a rigid framework, and in electronic communication with the reaction site through the flat but conjugated benzene ring. The diagrams show the para substituent. 

The reason for employing alternative treatments to ortho-substituted aromatic molecules is that changes in rate or ionization constants mediated by meta or para substituents are mostly changes in or because substitution does not affect AS or AS". Ortho substituents affect both enthalpy and entropy the effect on entropy is noteworthy because entropy is highly sensitive to changes in the size of reagents and substituents as well as degree of solvation. Bolton et al. examined the ionization of substituted benzoic acids and measured accurate values for AG, and A S... 

Doak. J. Am. Chem. Soc. 76, 1548-52 (1954). Dissociation constants for ortho substituted aromatic phosphonic acids. 

Dipole moment alcohols, phenols, and ortho substituted aromatics. 

Some ortho-substituted aromatic sulfonyl azides, like o-toluenesulfonyl azide (93), on thermolysis are converted into the corresponding sultams (94) (Scheme 60). The reaction probably involves intramolecular C—H bond insertion by the reactive o-toluenesulfonyl nitrene intermediate. The azide (N3- group also functions as a pseudohalide consequently,... 

The criteria for optimal activity were calculated to be free 5,7 OH groups and an ortho-substituted aromatic substituent at the 2-position of rohitukine. The most active compound selected, the 2 -chlorophenyl analogue of rohitukine (18), was originally called HL 275 but is now known as flavopiridol. A similar tyrosine kinase inhibitory effect had been noted in a series of flavonoid analogues although none of these were alkaloidal in nature [18]. 

The anomalies of ortho compounds are not restricted to their acidic strengths, but are found in all kinds of comparisons of the properties of related compounds. One of the first anomalies to be observed was the slower esterification of ortho substituted benzoic acids than of the corresponding meta and para acids This was attributed to the possibility of the physical interference of ortho groups, and was called steric hindrance. Fliirscheim, who early noted the anomalous strengths of ortho substituted aromatic acids, attributed the phenomenon to steric hindrance. He supposed that the ortho group... 

Any comparisons of the strengths of ortho substituted aromatic acids show an almost haphazard array of values such as those shown... 

This alkaloid is identical with glycosmine (156), the structure elucidation being accomplished by Pakrashi et al. (157). The uv spectrum has absorption maxima at 225, 265, 303 and 312 nm, while in the ir spectrum, the absorption bands at 1676 cm" and 1613 cm" suggest that the structure is a quinazolin-4-one substituted at position 2 and/or 3. An intense absorption at 770 cm is due to an ortho substituted aromatic ring. 

E° values, applicable to ortho-substituted aromatics have been determined from a study of the acid hydrolysis of o-substituted benzoates [11]. Charton [19, 23] has shown that values are independent of van der Waals radii and that steric effects are unimportant in both acid and basic hydrolysis of o-substituted benzoates. Any effect arising from a substituent was shown to be almost entirely due to resonance. He therefore concluded that does not in any way represent a steric effect. 

Ortho-substituted aromatic amides show atropisomerism as a result of the perpendicular orientation of the aryl and amide moieties. The non-biaryl atropisomers readily undergo racemization through rotation about the aryl-amide bond, indicating the possibility of DKR. For example, (S)-proline mediated addition of acetone to 2-formyl naphthamide gave a 2 1-5.5 1 diastereoisomer mixture with the optical purity of the major anti-isomer ranging from 86% to 91% ee (Scheme 5.24) [72]. 

The vinylcarbene complexes Cr(CX))5 =C(OEt)C=CXR) (X = NMe2, OEt R = alkyl, aryl) react with alkynes R OCH to form various cyclopenta[b]pyrans.30S In a two step process, addition of the alkynes NEt20Chfe u> the l-metalla-l,3-diene W(CX))s =C(OEt)CHsCHHi) results in metallatriene species that cyclise U) fwm cyclopentadiene complexes 40. Chromium Fischer type alkoxyalkenyl carbene complexes react with ketoalkynes to fcxm bicyclic lactones in a number of different processes involving 8 and 10-e cyclizations. Various dienyl carbene complexes whose parent in Crbenzannulation reaction involving alkyne cycloaddition with carbene complexes. ... 

Wong, 1973). Diol-containing resins used for the purpose of protection of aldehydes group via formation of the acetal were synthesized by Leznoff and Wong (1973) (Scheme 9-12). Although the resins readily formed acetals with m- and / -phthaldehyde, the highly hindered o-phthaldehyde and other ortho-substituted aromatic aldehydes as well as certain symmetrical aliphatic aldehydes failed to form acetals with this resin. In contrast, the 1,3-diol resin (Fig. 9-1) reacted with these less-reactive... 

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