Synthesis of tetrahydropyrans
The platinum-catalyzed hydroalkoxylation of γ- and δ-hydroxy olefins tolerated various substitution patterns and a number of functional groups including pivaloate and acetate esters, amides, silyl and benzyl ethers, and pendant hydroxyl and olefinic groups.
H. Qian, X. Han, R. A. Widenhoefer, J. Am. Chem. Soc., 2004, 126, 9536-9537.
The reaction of tertiary 1,4- and 1,5-diols with cerium ammonium nitrate at room temperature gives tetrahydrofuran and tetrahydropyran derivatives in high yield and stereoselectivity. Various fragrant compounds have been synthesized using this method.
E. J. Alvarez-Manzaneda, R. Chabouna, E. Alvarez, E. Cabrera, R. Alvarez-Manzaneda, A. Haidour, J. M. Ramos, Synlett, 2006, 1756-1758.
Lanthanide triflates are efficient catalysts for the intramolecular Markovnikov-type hydroalkoxylation/cyclization of primary/secondary and aliphatic/aromatic hydroxyalkenes in room temperature ionic liquids (RTILs) to give five- and six-membered oxygen heterocycles in very good yields.
A. Dzudza, T. J. Marks, Org. Lett., 2009, 11, 1523-1526.
Silver(I) triflate catalyzes intramolecular additions of hydroxyl or carboxyl groups to olefins in good to excellent yields for a range of substrates under relatively mild conditions. This reaction is one of the simplest methods to construct cyclic ethers or lactones.
C.-G. Yang, N. W. Reich, Z. Shi, C. He, Org. Lett., 2005, 7, 4553-4556.
The Au(I)-catalyzed intramolecular hydroamination of N-allenyl carbamates was effective for the formation of various cyclic amines. γ-Hydroxy and δ-hydroxy allenes underwent Au-catalyzed intramolecular hydroalkoxylation to form the corresponding oxygen heterocycles in good yield. 2-Allenyl indoles underwent Au-catalyzed intramolecular hydroarylation to form 4-vinyl tetrahydrocarbazoles in good yield.
Z. Zhang, C. Liu, R. E. Kinder, X. Han, H. Qian, R. A. Widenhoefer, J. Am. Chem. Soc., 2006, 128, 9066-9073.
A mild and convenient free-radical cyclization of organohalides in the presence of a NiCl2 • DME/Pybox complex as the catalyst and zinc powder in methanol efficiently gives carbo-, oxa-, and azacycles as products in high yields from unsaturated alkyl halides.
H. Kim, C. Lee, Org. Lett., 2011, 13, 2050-2053.
Key step of an eco-friendly and highly diastereoselective synthesis of substituted cis-2,6-piperidines and cis-2,6-tetrahydropyrans is an iron-catalyzed thermodynamic equilibration of 2-alkenyl 6-substituted piperidines and 2-alkenyl 6-substituted tetrahydropyrans allowing the isolation of enriched mixtures of the most stable cis-isomers.
A. Guérinot, A. Serra-Muns, C. Gnamm, C. Bensoussan, S. Reymond, J. Cossy, Org. Lett., 2010, 12, 1808-1811.
The gold(I)-catalyzed cyclization of chiral monoallylic diols to form tetrahydropyrans is highly stereoselective. Substrates that differ only in olefin geometry provide enantiomeric products from formal SN2′ reactions in high yields with excellent chirality transfer. The allylic alcohol stereochemistry also efficiently controls the facial selectivity when the substrates include additional stereocenters.
A. Aponick, B. Biannic, Org. Lett., 2011, 13, 1330-1333.
2-(Arylmethylene)cyclopropylcarbinols could be converted to the corresponding tetrahydropyrans stereoselectively in the presence of Brønsted acids under mild conditions. A plausible Prins-type reaction mechanism has been proposed.
G.-Q. Tian, M. Shi, Org. Lett., 2007, 9, 2405-2408.
Exo-3-furanylidenes and 3-pyranylidenes products having cis-2,5 and cis-2,6 substitution were synthesized from terminally substituted alkynyl alcohols with various aldehydes via Prins-type cyclization and trapping of the resulting vinyl cations as vinyl triflates in good yields. Vinyl triflates underwent a subsequent stereoselective hydrolysis to give the corresponding 3-acyl-substituted products.
S. N. Chavre, H. Choo, J. K. Lee, A. N. Pae, Y. Kim, Y. S. Cho, J. Org. Chem., 2008, 73, 7467-7471.
Cyclization of δ-halocarbanions to cyclobutanes is a relatively slow process, thus formation of tetrahydropyran derivatives via addition to aldehydes and subsequent cyclization is possible in high yield. A simple mechanistic discussion, optimization of the reaction conditions, and the scope of the reaction are discussed.
M. Barbasiewicz, A. Brud, M. Mąkosza, Synthesis, 2007, 1209-1213.
Phosphomolybdic acid catalyzes efficiently the Prins cyclization of homoallylic alcohols with aldehydes in water at room temperature to provide tetrahydropyran-4-ol derivatives in high yields with all cis-selectivity. The use of phosphomolybdic acid in water makes this procedure simple, convenient, cost-effective, and environmentally friendly.
J. S. Yadav, B. V. S. Reddy, G. G. K. S. N. Kumar, S. Aravind, Synthesis, 2008, 395-400.
The rhenium(VII) complex O3ReOSiPh3 is a particularly effective catalyst for Prins cyclizations using aromatic and α,β-unsaturated aldehydes. The reaction conditions are mild, and the highly substituted 4-hydroxytetrahydropyran products are formed stereoselectively.
K. Tadpetch, S. D. Rychnovsky, Org. Lett., 2008, 10, 4839-4842.
1-n-Butyl-3-methylimidazolium chloroaluminate [bmin]Cl . AlCl3 was successfully employed as a reaction medium for Prins cyclizations, to produce 4-chlorotetrahydropyran derivatives in short reaction times.
J. S. Yadav, B. V. S. Reddy, M. S. Reddy, N. Niranjan, A. R. Prasad, Eur. J. Org. Chem., 2003, 1779-1783.
Aldehydes undergo rapid and selective coupling with 3-buten-1-ol in the presence of 20 mol% of niobium(V) chloride to afford 4-chlorotetrahydropyran derivatives under extremely mild conditions in excellent yields. Similar halogenated tetrahydropyrans are also obtained using gallium(III) halides.
J. S. Yadav, B. V. Subba Reddy, M. K. Gupta, S. K. Biswas, Synthesis, 2004, 2711-2715.
An efficient method allows the construction of 2,6-cis-4,5-dibromo-tetrasubstituted tetrahydropyran rings with well-controlled stereochemistry in good yields.
F. Liu, T.-P. Loh, Org. Lett., 2007, 9, 2063-2066.
A highly stereoselective route to 2,4,5-trisubstituted tetrahydropyrans employs an intramolecular allylation of a (Z)-allylsilane onto an aldehyde under Brønsted acid activation.
P. J. Jervis, B. M. Kariuki, L. R. Cox, Org. Lett., 2006, 8, 4637-4640.
A new convergent synthetic approach to the 2-hydroxypyran motif common to many naturally occurring structures includes the esterification of two fragments and a subsequent intramolecular reductive cyclization.
L. V. Heumann, G. E. Keck, Org. Lett., 2007, 9, 1951-1954.
An intramolecular iodo-aldol cyclization of prochiral α-substituted enoate aldehydes and ketones produces hetero- and carbocycles containing quaternary centers adjacent to secondary or tertiary centers. The reactions occur in good yields and are highly trans-selective with hydroxyl and iodomethyl groups on opposite faces of the ring system.
F. Douelle, A. S. Capes, M. F. Greaney, Org. Lett., 2007, 9, 1931-1934.
A comparative study of chiral Mo- and Ru-based catalysts to promote enantioselective synthesis of 2,6-disubstituted pyrans and piperidines through asymmetric ring-opening/cross-metathesis reactions demonstrated the critical complementarity that exists between the two classes of chiral catalysts.
G. A. Cortez, C. A. Baxter, R. R. Schrock, A. H. Hoveyda, Org. Lett., 2007, 9, 2871-2874.
Treatment of 3-[(alkoxycarbonyl)alkyl]-substituted conjugated cycloalkenones with diisobutylaluminum hydride at -78 °C followed by acid quenching furnishes spiro ethers, whereas the corresponding 3-(carboxyalkyl)-substituted cycloalkenones generate spiro lactones upon reaction with sodium borohydride at 30 °C followed by acid quenching.
M.-C. P. Yeh, Y.-C. Lee, T.-C. Young, Synthesis, 2006, 3621-3624.
The first enantioselective intramolecular catalytic Stetter reaction, which opens up a short and efficient pathway to enantiomerically enriched chroman-4-ones, is reported.
D. Enders, K. Breuer, J. Runsink, Helv. Chim. Acta, 1996, 79, 1899-1902.
An efficient and regioselective Yb(OTf)3-promoted palladium-catalyzed oxidative cyclization of γ-heteroalkenyl β-keto amides has been developed. Under simple aerobic condition, various six-, seven-, and eight-membered-ring N- and O-heterocycles were obtained in excellent yield.
K.-T. Yip, J.-H. Li, O.-Y. Lee, D. Yang, Org. Lett., 2005, 7, 5717-5719.
A direct Pd-catalyzed arylation reaction for the intramolecular formation of biaryl compounds using a novel phosphine ligand offers enhanced catalytic activity for transformations of previously unreactive substrates.
L.-C. Campeau, M. Parisien, M. Leblanc, K. Fagnou, J. Am. Chem. Soc., 2004, 126, 9186-9187.
Diastereoselective and Enantioselective Construction of Cyclic Ethers
Stereocontrolled Construction of Cyclic Ethers
Enantioselective Construction of Naturally-Occurring Cyclic Ethers