Alcohols reaction modes

Iodorhodium(III) porphyrins generally lead to alkylrhodium(III) porphyrins (Scheme 42)398>. This is also true for the reaction with ethyl diazoacetate in the presence of HOAc or an alcohol, and the insertion product 412 (M = Rh) could not be detected, in contrast to the corresponding cobalt porphyrin. A mechanistic scheme, which includes the diverse reaction modes of metalloporphyrins towards diazo compounds, has been proposed by Callot 393,398). 

Despite the fact that /-eliminations are frequent reaction modes for cyclobutanes, because Cl and C3 are only separated by approximately 2.1 A, only -elimination of hydrogen fluoride is found for the reaction between 3,3-difluorocyclobutane-l-carbonitrile (27) and a variety of bases such as ferf-butoxide in diethyl ether, ferf-butoxide in /er/-butyl alcohol and sodium hydride in tetrahydrofuran.10... 

Oxidation of organic compounds by ruthenium tetraoxide has been reviewed. The oxidation of various types of organic compounds such as alkanes, alkenes, allenes, aromatic rings, alcohols, amines, and sulfides has been discussed The cyclic oxoruthe-nium(VI) diesters that are formed in the initial step of the oxidation of alkenes are considered to be intermediates in the formation of 1,2-diols.70 The development of new and selective oxidative transformations under ruthenium tetroxide catalysis during the past 10 years has been reviewed. The state of research in this field is summarized and a systematic overview of the reactivity and the reaction mode of ruthenium tetroxide is given.71... 

Lanthanide alkyl and aryl complexes can readily react with a range of substrates with acidic protons, such as alcohols, phenols, phenylacetylene, and amine, to be converted into the corresponding lanthanide derivatives. Lanthanide alkyl complexes react with H2 to form the corresponding hydride complex, which is the popular route to lanthanide hydride. Various unsaturated small molecules can insert into an Ln-alkyl bond to form the derivates containing Ln-heteroatom bonds. The reaction modes found are summarized in Figure 8.14 [59-62]. 

In contrast to the reaction mode of the propargyl ethers, a,/3-unsaturated aldehydes and ketones are isolated in the catalytic isomerization of the propargyl alcohols. Trost et al. developed a new catalytic system, (IND)RuCl(PPh3)2/InCl3/ NH4PF13/THF (IND = -indenyl), that efficiently effected such isomerization [14]. The reaction is cocatalyzed by a mixture of NHEtBPFj and NH4PF6, and addition of indium trichloride accelerates the reaction (Eq. 12.9). 

Esters, Ethers, and Related Derivatives of Alcohols.— The mode of transmission of the effect of remote substituents upon reaction rates and equilibria has been discussed previously under three headings, viz. inductive effects, electrostatic field effects, and conformational transmission.A new survey,quoting over 50 references, covers most of the main studies in this field, and suggests direct interactions as a fourth class. Rates of acetylation of 3j3-hydroxy-A"-steroids variously substituted at C-17 show only small variations, which did not permit of any mechanistic interpretation. The formation of 17a,20- and 20,21-cyclic carbonates and their use as protecting groups for diols have been investigated. ... 

The nature of exchange mechanism with secondary alcohols will depend on the stability of the intermediate carbonium ion and possibly alcohols possessing an alpha-phenyl substituent simulate the reaction mode of tertiary alcohols, whereas the simple secondary alkyl alcohols possibly utilise a mechanism similar to that of the primary substrates. The extensive kinetic investigations of Manassen and Klein on the dehydration of secondary butanol have been interpreted in terms of carbonium-ion intermediates which are symmetrically solvated. Supporting evidence for this idea is provided by the earlier studies on the rate of exchange of 0 in optically active secondary butanol Race-... 

The basicity and nucleophilicity of incarcerated lithium alcoholates exceeds those of bulk phase alcoholates by several orders of magnitude resulting in efficient inner-molecular elimination or nucleophilic transacetalisation and formation of hemi-carcerands with one extended portal. In these innermolecular reactions, small structural changes of the guest have a sound effect on the reaction mode. 

Chlorosulfonic acid (CSA) sulfation of alcohols or alcohol ethoxylates is usually conducted in batch reaction mode, typically in glass-lined vessels, but requires little or no excess reagent to drive the reaction to completion and can be conducted in a continuous liquid-liquid contacting process. The reaction evolves a stoichiometric quantity of HCl gas, which can be captured either as an HCl solution or with caustic to yield sodium chloride. Product color, yield, and quality cau be very high, but throughput efficiency is modest in batch mode. 

Figure 9-1 depicts a variety of reaction modes available to alcohols. Usually at least one of the four bonds marked a, b, c, or d is cleaved. In Chapter 8 we learned that oxidation to aldehydes and ketones breaks bonds a and d. We found that the use of this reaction in combination with additions of organometallic reagents provides us with the means of preparing alcohols of considerable structural diversity. 

Figure 9-1 Four typical reaction modes of alcohols. In each mode, one or more of the four bonds marked a-d are cleaved (wavy line denotes bond cleavage) (a) deprotonation by base (fa) protonation by acid followed by uni- or bimolecular substitution (fa, c) elimination and (a, d) oxidation.

Interfacially active guanidinium-thiourea bifunctional catalyst 190 catalyzes highly enantioselective nitroaldol reactions in the presence of an external base such as KOH in toluene/water biphasic conditions. Although the retro-nitroaldol reactions generally proceed under basic conditions, addition of KI inhibits the retro-process. A cooperative reaction mode between guanidinium and thiourea moieties is supported by experiments using structural variants of 190. A positive nonlinear effect is observed between the enantiomeric excess of 190 and the product 191. These results support the hypothesis that self-a egation of 190 is necessary for catalysis (Scheme 28.22) (96, 97). Catalyst 190 has been used in the synthesis of chiral tertiary alcohol products obtained in nitroaldol reactions of nitroalkanes and a-ketoesters [98],... 

Primary aromatic amines differ from primary aliphatic amines in their reaction with nitrous acid. Whereas the latter yield the corresponding alcohols (RNHj — ROH) without formation of intermediate products see Section 111,123, test (i), primary aromatic amines 3neld diazonium salts. Thus aniline gives phcnyldiazonium chloride (sometimes termed benzene-diazonium chloride) CjHbNj- +C1 the exact mode of formation is not known, but a possible route is through the phenjdnitrosoammonium ion tlius ... 

Fonnation of allylic products is characteristic of solvolytic reactions of other cyclopropyl halides and sulfonates. Similarly, diazotization of cyclopropylamine in aqueous solution gives allyl alcohol. The ring opening of a cyclopropyl cation is an electrocyclic process of the 4 + 2 type, where n equals zero. It should therefore be a disrotatory process. There is another facet to the stereochemistry in substituted cyclopropyl systems. Note that for a cri-2,3-dimethylcyclopropyl cation, for example, two different disrotatory modes are possible, leading to conformationally distinct allyl cations ... 

An interesting alcoholysis of epoxides has been reported by Masaki and coworkers <96BCSJ195>, who examined the behavior of epoxides in the presence of a catalytic amount of the Tt-acid tetracyanoethylene (TCNE, 85) in alcoholic media. Ring-opening is very facile under these conditions, typically proceeding via normal C-2 attack, as exemplified by styrene oxide (86). Certain epoxy ethers (e.g., 89) undergo C-1 attack due to anchimeric assistance. Analysis of the reaction mixtures revealed the presence of captodative ethylenes (e.g., 85) formed in situ, whieh were shown to be aetive in eatalyzing the reaction. The proposed mode of catalysis is represented by the intermediate 87. The affinity of these captodative olefins for... 

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