Alcohol-based synthesis

An ingenious multi-step synthesis of oxo[l,3]thiazolo[5,4-/]azocine 214 is based on the transformations of ethyl tetrahydro[l,3]benzothiazolyl acetate 209 (81CPB1780 Scheme 59). Under the action of methylamine, 209 cyclizes to thiazolo[4,5-e]indolone 210 which, through compounds 211 and 212, converts into quaternary salt 213. The key stage of the process is the efficient rearrangement of this salt into thiazoloazocine under the action of alcoholic base. 

This method involves formation of reverse micelles in the presence of surfactants at a water-oil interface. A clear homogeneous solution obtained by the addition of another amine or alcohol-based cosurfactant is termed a Microemulsion. To a reverse micelle solution containing a dissolved metal salt, a second reverse micelle solution containing a suitable reducing agent is added reducing the metal cations to metals. The synthesis of oxides from reverse micelles depends on the coprecipitation of one or more metal ions from... 

Webster et al. l4a expanded on the preparation of the polyphenylenes to develop the one-pot synthesis of hyper-crosslinked poly(triphenylcarbinol). Thus, reaction of 4,4 -dilithiobiphenyl with (CH3)2C03 (— 80 °C — 25 °C, THF) afforded trityl alcohol-based polymer. The absence of carbonyl or methoxycarbonyl NMR resonances led to the speculation that the polymer grows via a branched convergent process. 

Scheme 44 General synthesis of allylic alcohols based on a-a]k)4ation of allylic sulfoxides followed hy [2,3]-sigmatropic rearrangement...

A recent synthesis of the tricyclic secoiridoid ( )-sarracenin (98) relied on the Patemo-Biichi addition of acetaldehyde and cyclopentadiene as the initial step. Irradiation of cyclopentadiene and acetaldehyde provided a 5 1 mixture of bicyclic oxetanes (97) and (96) in 5-10% yield. Treatment of the crude photolysate with CSA and methanol followed by tosylation of the cmde product gave (99), which represents the toluenesulfonate ester derived from the major oxetane (97). The tosylate was displaced by the anion prepared from dimethyl 3-styrenylmalonate to afford the substituted malonate (100) in 84% yield (Scheme 10). Attempts to effect ring opening of the oxetane mixture were unsuccessful. Decarboxylation and demethylation gave the alcohol (102) which was subjected to ozonolysis and reductive work-up to afford ( )-sarracenin in 60% yield. The oxetane-based synthesis is noteworthy due to its brevity and use of a biosynthetically postulated trialdehyde equivalent. 

The preparation of alkenic alcohols based on rDA processes has found application in the synthesis of natural products. Matsutake alcohol (14a (-)-( )-l-octen-3-ol), an important flavor component of mushrooms, can be prepared in high enantiomeric purity by a method that includes rDA cleavage as a key step. Asymmetric DA addition gave enantiomerically pure adducts that were modified dia-... 

Loh et al have demonstrated the stereoselective synthesis of 1,3-amino alcohols based on the InCla-catalyzed Mukaiyama aldol reaction of a keto ester under solvent-free conditions. The high selectivity has been explained by the influence of a remote group present in the keto ester (Scheme 5.45). 

A similar intramolecular hydroacylation is possible via reductive radical aldehyde addition to alkencs and subsequent oxidation of the resulting alcohol. Based on this observation a strategy towards the synthesis of cuparenoids [( )-a-cuparenone. ( )-epilaurene and laurene] was... 

PAN Pan, Y., Xiao, H., Zhao, G., and He, B., Synthesis and characterization of temperature-responsive poly(vinyl alcohol)-based copolymers, J. Appl. Polym. Sci., no, 2698, 2008. 

Diinethoi iisphthaleiie (I) is reduced with sodium and alcohol to the ketone (II), methylated with methyl iodide, and then subjected to the Robinson-Mannich base synthesis yielding the phenanthrene derivative (III). Demethylation, reduction of the a,j3-unsaturated ketone system, and partial acetylation produces IV, which is then hydrogenated under... 

Lee CK, Lee CA, Tan K, Loh T (2004) An Unusual Approach to the Synthesis of Enantiomerically Cis Linear Homoallylic Alcohols Based on the Steric Interaction Mechanism of Camphor Scaffold. Org Lett 6 1281... 

Hayashi Y, Urnshima T, Shin M, Shoji M (2005) The Stereoselective Synthesis of a-Substituted P-Amino Secondary Alcohols Based on the Proline-Mediated, Asymmetric, Three-Cranptment Mannich Reaction and its Application to the Formal Total Synthesis of Nikkranycins B and Bx. Tetrahedron 61 11393... 

Hartung, J. and Greh, M. (2002) Transition metal-catalyzed oxidations of bishomoallyhc alcohols. J. Organomet. Chem., 661,67-84 (b) Hartung, J., Drees, S., Greh, M., Schmidt, P., Svoboda, 1., Fuess, H., Murso, A., and Stalke, D. (2003) (SchifF-base)vanadium(V) complex-catalyzed oxidations of substituted bis(homoallylic) alcohols -Stereoselective synthesis of functionalized tetrahydrofurans. Eur. J. Org. Chem., 2388-2408. 

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