Carbinols substitution with

The rather complex furylvinylcarbinol derivative 76 shown in Scheme 4.28 was required in enantiopure form as a key intermediate in the synthesis of the natural product cneorin. The carbinol moiety is heavily substituted with sterically demanding groups. Therefore attempts to resolve the furylvinylcarbinol with CALB or lipase PS-II led to very slow reactions. However, the rarely used enzyme Candida antarctica lipase A (CALA), which is known to act on sterically hindered substrates offers an alternative. Thus acylation of the furylvinylcarbinol 76 with 2,2,2-trifluoroethyl butanoate catalyzed by CALA (immobilized on celite with sucrose at pH 7.9) furnished the enantiomerically enriched propanoate of S-76 and R-76 (Scheme 4.28) [90]. Small-scale experiments gave E > 300. 

Hydrocoupling of aldehydes and ketones with pyridine during reduction is a facile process. The products are piperidyl carbinols substituted in the 2- or 4-position of the ring. They can also have a double bond at the 3-position (Scheme 3). Different workers reported varying amounts of the possible... 

Other alkylation reactions are observed in the condensation of cyclo-propanium ions (generated in situ) with ketones 89.92)> enamines6, nitroalkanes 93>, dimethylmalonate 92>, and phenol. 92> Thus, 7-hydroxy-7-pyrrolidinobicyclo[4.1.0]heptane (56) as well as the 7,7-dipyrrolidino derivative (54) react with acetone to give the amino ketone 113. 89> This reaction may be pictured as an addition of the enol form of the ketone to the reactive iminium salt formed from the carbinol amine. In like manner, phenol undergoes ortho substitution with the carbinol amine 114 formed from cyclopropanone and dimethyl amine. 

Oxidation of the carbinol (4) with periodate does not give the expected iro-epoxy compound but the benzaldehyde acetal of 3,5-di-t-butylcatechol (5). This oxidative rearrangement is apparently limited to o-hydroxy-substituted diaiyl- and triaryl-carbinols. ... 

Prodncts of 2- and 4-snbstitntion of hydrogen are obtained by reaction of the sodium salt of imidazole with the phenyl pyrimidin-5-yl carbinol mesylate, with none of the product of direct substitution. Similar resnlts are obtained with the sodium salts of pyrrole and indole, but other nucleophiles, such as amines, give complex product mixtures. " ... 

Miscellaneous Reactions of LR. Under particular conditions, certain carbonyl compounds and other substrates react with LR to form thiophosphonates or heterocycles, which fact throws some hght on the mechanism of thionation reactions with LR. Carbinols undergo nucleophilic substitution with LR to form the corresponding thiols. The redox properties of LR can be utilized to prepare dithiolactones from dialdehydes (eq 22), a-0X0 thioamides from nitro ketones (eq 23), or sulfides from sulfoxides. ... 

Without additional reagents Substitution with carbinols... 

Reactions which almost certainly involve 2-substitution by a carbonium ion are those between pyrrole and a triaryl carbinol, or with xanthydrol in acetic acid. Triaryl chlorides also cause 2-substitution by a carbonium ion... 

The simplest method for the addition of a 2-carbon fragment to a 17-keto steroid while retaining an oxygen function at C-17 is via reaction with acetylene or a substituted acetylene e.g., ethoxyacetylene, chloroacetylene). Since the resulting acetylenic carbinol (which is usually obtained in excellent yield) can in turn be hydrated, reduced, rearranged, and oxidized, this reaction offers considerable synthetic possibilities. 

The nitrites aie most conveniently prepared from the corresponding alcohols by treatment with nitrosyl chloride in pyridine. The crude nitrites can be precipitated by addition of water and recrystallized from appropriate solvents. However nitrites prepared from carbinols in which the adjacent carbon is substituted by halogen, free or esterified hydroxyl or a carbonyl function are very readily hydrolyzed and must be recrystallized with great care. In general the photolysis gives higher yields if purified and dried nitrites are used which do not contain acids or pyridine, although occasionally the addition of small amounts of pyridine is recommended in order to prevent hydrolysis of the nitrite. Traces of acids do in fact catalyze the thermal decomposition of secondary nitrites to equimolar amounts of alcohol and ketone. ... 

The palladium-catalyzed reaction of o-iodoanilides with terminal acetylenic carbinols provides a facile route to the synthesis of quinolines using readily available starting materials (93TL1625). When o-iodoanilide 126 was stirred with acetylenic carbinol 127 in the presence of bis-triphenyl phosphine palladium(ll) chloride in triethylamine at room temperature for 24 h, the substituted alkynol 128 was obtained in 65% yield. On cyclization of 128 with sodium ethoxide in ethanol, 2-substituted quinoline 129 was obtained in excellent yield. 

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