Problematic alcohols

This class of substrate is the only real problematic substrate for the AE reaction. The enantioseleetivity of the AE reaction with this class of substrate is often variable. In addition, rates of the catalytic reactions are often sluggish, thus requiring stoichiometric loadings of Ti/tartrate. Some representative product epoxides from AE reaction of 3Z-substituted allyl alcohols are shown below. 

The simple and elegant tactic of cleaving the acetoxythioacetal function in 29 either with or without concomitant epimerization at C-2 effectively avoids the problematic (nonstereoselective) epoxi-dation of chiral Z allylic alcohols such as 12-Z (see Scheme 9). 

Antipsychotics are not indicated for the treatment of withdrawal, except when hallucinations or severe agitation are present (Naranjo and Sellers 1986), in which case they should be added to a benzodiazepine. In addition to their potential to produce extrapyramidal side effects, antipsychotics lower the threshold for seizures, which is particularly problematic during alcohol withdrawal. 

Choice of LEL The median experimental value (1.1 %) seems to be the most relevant. Hilado s method is problematic the choice is between a = 0.476 (alcohols) and a = 0.537 (ethers)... 

The ketone 15 was eventually prepared by Grignard addition to Weinreb amide 21, as shown in Scheme 5.5. The Weinreb amide 21 was prepared from p-iodobenzoic acid (20). The phenol of readily available 3-hydroxybenzaldehyde (22) was first protected with a benzyl group, then the aldehyde was converted to chloride 24 via alcohol 23 under standard conditions. Preparation of the Grignard reagent 25 from chloride 24 was initially problematic. A large proportion of the homo-coupling side product 26 was observed in THF. The use of a 3 1 mixture of toluene THF as the reaction solvent suppressed this side reaction [7]. The iodoketone 15 was isolated as a crystalline solid and this sequence was scaled up to pilot plant scale to make around 50 kg of 15. 

Mononuclear amidinate tin(II) alkoxides, (282) and (283), have also been examined the latter consumes 92 equivalents rac-LA over 165 min in toluene at 80 °C (Mn calc = 28,900, Mn calc= 14400, Mw/Mn= 1.18).859 Reproducibility of the polymer chain length is problematic, but the addition of 1 equivalent of an alcohol serves to deliver greater control. Kinetic studies reveal that the rate law is 0.33 ( 0.02) in [Sn], suggesting that aggregation of the active species may occur. 

The final cyclization manifold has been realized with a different ruthenium catalyst (Scheme 22). The cationic [Cp Ru(MeCN)3]PF6 induces exclusive endo-dig cyclization of both homopropargylic and bis-homopropargylic alcohols.29 73 The clean reaction to form a seven-membered ring is noteworthy for several reasons intramolecular exo-dig cyclization with bis-homopropargylic alcohols is not well established, the platinum-catalyzed case has been reported to be problematic,80 and the selectivity for seven-membered ring formation over the exo-dig cyclization to form a six-membered ring is likely not thermodynamic. The endo-dig cyclization manifold was thus significant evidence that a re-examination of alkyne hydrosilylation mechanisms is necessary (see Section 10.17.2). 

Establishing the elemental composition based on the isotopic peaks may be problematic if, for example, the sample contains impurities with the masses in the region of the molecular ion cluster. In the El mass spectra of amines, alcohols, acids, and some other classes of organic compounds there is often a peak of [M + H]+ ion. It distorts the isotopic picture. It is worth mentioning as well that in real experimental conditions the peak intensity may vary slightly in each... 

The presence of strongly nucleophilic groups in either the donor or the acceptor can be problematic in sulfoxide-type glycosylations when activation is conducted with triflic anhydride. The most common culprit is the amide group [340,341], which is illustrated by the formation of a dihydrooxazine when a 3-acetamido alcohol was employed as acceptor (Scheme 4.47) [342]. Self-evidently, acceptor-based problems of this type could be avoided by the preactivation of the sulfoxide with triflic anhydride. 

Easton C, Bauer LO. (1997). Neuropsychological differences between alcohol-dependent and cocaine-dependent patients with or without problematic drinking. Psychiatry Res. 71(2) 97-103. 

Substance-Induced Anxiety Disorder. Numerous medicines and drugs of abuse can produce panic attacks. Panic attacks can be triggered by central nervous system stimulants such as cocaine, methamphetamine, caffeine, over-the-counter herbal stimulants such as ephedra, or any of the medications commonly used to treat narcolepsy and ADHD, including psychostimulants and modafinil. Thyroid supplementation with thyroxine (Synthroid) or triiodothyronine (Cytomel) can rarely produce panic attacks. Abrupt withdrawal from central nervous system depressants such as alcohol, barbiturates, and benzodiazepines can cause panic attacks as well. This can be especially problematic with short-acting benzodiazepines such as alprazolam (Xanax), which is an effective treatment for panic disorder but which has been associated with between dose withdrawal symptoms. 

Side effects of benzodiazepines include drowsiness and reduced respiratory function. In patients who are severely medically ill, especially those with lung disease, this side effect can be problematic. However, benzodiazepines are much safer in this regard than their predecessors, the barbiturates, and untreated delirium tremens, the most severe form of alcohol withdrawal, can be fatal. 

Movassaghi and Schmidt reported that amidation of unactivated esters also occurs in the presence of carbene 3 when 1,2-amino alcohols are nsed [138], A representative sample of the range of esters 277 and amino alcohols 278 is shown in Table 24. A few snbstrates proved problematic under standard reaction conditions. 

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