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Reactions >> Protecting Groups >> Stability

1,3-Dithianes, 1,3-Dithiolanes

T. W. Green, P. G. M. Wuts,
Protective Groups in Organic Synthesis,
Wiley-Interscience, New York, 1999, 329-344, 724-727.



H2O: pH < 1, 100°C pH = 1, RT pH = 4, RT pH = 9, RT pH = 12, RT pH > 12, 100°C
Bases: LDA NEt3, Py t-BuOK Others: DCC SOCl2
Nucleophiles: RLi RMgX RCuLi Enolates NH3, RNH2 NaOCH3
Electrophiles: RCOCl RCHO CH3I Others: :CCl2 Bu3SnH
Reduction: H2 / Ni H2 / Rh Zn / HCl Na / NH3 LiAlH4 NaBH4
Oxidation: KMnO4 OsO4 CrO3 / Py RCOOOH I2, Br2, Cl2 MnO2 / CH2Cl2


1,3-Dithianes and 1,3-dithiolanes can easily be prepared from carbonyl compounds with 1,3-propanedithiol or 1,2-ethanedithiol in the presence of a Brönsted or a Lewis acid catalyst. Removal of a dithiane protection group often requires harsh conditions and is usually performed in the late synthetic stage.

Summary of the use of 1,3-dithianes in synthesis

Protection of Carbonyl Compounds

A Lewis acid-surfactant-combined copper bis(dodecyl sulfate) [Cu(DS)2] catalyst served as an efficient and reusable catalyst for the thioacetalization and transthioacetalization of carbonyl compounds and O,O-acetals in water at room temperature. This procedure offers high chemoselectivity, ease of operation and purification without any organic solvent, and high yields.
S.-S. Weng, S.-C. Chang, T.-H. Chang, J.-P. Chyn, S.-W. Lee, C.-A. Lin, F.-k. Chen, Synthesis, 2010, 1493-1499.

Carbonyl compounds have been successfully converted into their corresponding oxathiolane, dithiolane, and dithiane derivatives with 2-mercaptoethanol, 1,2-ethanedithiol, and 1,3-propanedithiol using a catalytic amount of yttrium triflate. In addition, by using this catalyst, highly chemoselective protection of aldehydes has been achieved.
S. K. De, Tetrahedron Lett., 2004, 45, 2339-3241.

Tungstophosphoric acid (H3PW12O40) was found to be an effective and highly selective catalyst for the thioacetalization of aldehydes, ketones, acetals, acylals and O,S-acetals in excellent yields in the absence of solvent. Chemoselective conversions of α- or β-diketones and a β-keto ester are described. Sterically hindered carbonyl compounds were converted to the corresponding thioacetals in refluxing petroleum ether in good yields.
H. Firouzabadi, N. Iranpoor, K. Amani, Synthesis, 2002, 59-60.

Aldehydes and ketones were protected as their thioacetals in the presence of a catalytic amount of iodine. These mild reaction conditions were also applied in the transthioacetalization of O,O-acetals, O,O-ketals and O,S-acetals and acylals.
H. Firouzabadi, N. Iranpoor, H. Hazarkhani, J. Org. Chem., 2001, 66, 7527-7529.

A new procedure for the protection of aldehydes and ketones as thioacetals promoted by catalytic amount of p-toluenesulfonic acid and silica gel has been developed. This procedure offers versatility, short reaction time, excellent yield, and is easy to carry out. A simple filtration followed by removal of solvent in most cases produces pure product.
M. H. Ali, M. G. Gomes, Synthesis, 2005, 1326-1332.

Perchloric acid adsorbed on silica gel (HClO4-SiO2) has been found to be an extremely efficient and reusable catalyst for 1,3-dithiolane and 1,3-dithiane formation under solvent-free conditions at room temperature.
S. Rudrawar, R. C. Besra, A. K. Chakraborti, Synthesis, 2006, 2767-2771.

Praseodymium triflate is an efficient and recyclable catalyst for chemoselective protection of aldehydes.
S. K. De, Synthesis, 2004, 2837-2840.

A catalytic amount of a water-stable Brønsted acidic ionic liquid with an alkane sulfonic acid catalyzed a mild and chemoselective thioacetalization of various aldehydes to afford 1,3-dithianes in very good yield and short reaction times.
A. R. Hajipour, G. Azizi, A. E. Ruoho, Synlett, 2009, 1974-1978.

Various carbonyl compounds including aliphatic and aromatic aldehydes and ketones were converted to the corresponding thioacetals in high yields in the presence of a catalytic amount of hafnium trifluoromethanesulfonate. The mild conditions tolerated various sensitive functional and protecting groups and were racemization-free when applied to R-aminoaldehydes.
Y.-C. Wu, J. Zhu, J. Org. Chem., 2008, 73, 9522-9524.

A catalytic dithioacetalization of aldehydes in the presence of iron catalyst provides access to 1,3-dithianes using 2-chloro-1,3-dithiane under mild conditions. This highly efficient dithioacetaliation process results in good to excellent yields.
J. Lai, W. Du, L. Tian, C. Zhou, X. She, S. Tang, Org. Lett., 2014, 16, 4396-4399.

As a non-thiolic, odorless propane-1,3-dithiol equivalent, 3-(1,3-dithian-2-ylidene)pentane-2,4-dione has been investigated in acid-promoted thioacetalization under solvent-free conditions. A range of selected aldehydes and aliphatic ketones have been converted into the corresponding dithioacetals in high yields. The relatively slow reaction rate of aromatic ketones allows chemoselective protection.
Y. Ouyang, D. Dong, C. Zheng, H. Yu, Q. Liu, Z. Fu, Synthesis, 2006, 3801-3804.

3-(1,3-dithian-2-ylidene)pentane-2,4-dione has been used as a nonthiolic, odorless 1,3-propanedithiol equivalent in the p-dodecylbenzenesulfonic acid-catalyzed thioacetalization of various aldehydes and ketones in water.
D. Dong, Y. Ouyang, H. Yu, Q. Liu, J. Liu, M. Wang, J. Zhu, J. Org. Chem., 2005, 70, 4535-4537.

Other Syntheses of Dithianes

-Keto 1,3-dithianes can be generated by the double conjugate addition of dithiols to propargylic ketones, esters and aldehydes in excellent yields. These masked 1,3-dicarbonyl systems can be converted to a range of functionalised oxygen-containing heterocycles that can be used in natural product synthesis.
M. J. Gaunt, H. F. Sneddon, P. R. Hewitt, P. Orsini, D. F. Hook, S. V. Ley, Org. Biomol. Chem., 2003, 1, 15-16.

Aldehydes and ketones were protected as their thioacetals in the presence of a catalytic amount of iodine. These mild reaction conditions were also applied in the transthioacetalization of O,O-acetals, O,O-ketals, O,S-acetals, and acylals.
H. Firouzabadi, N. Iranpoor, H. Hazarkhani, J. Org. Chem., 2001, 66, 7527-7529.

An oxidative coupling method for alkyne difunctionalization under metal-catalyst-free conditions affords various β-ketodithianes in very good yields with high regioselectivities. The reaction provides valuable dithianes with controlled formation of a new C-C bond and a C-O bond via a radical coupling pathway.
J. Lai, L. Tian, X. Huo, Y. Zhang, X. Xie, S. Tang, J. Org. Chem., 2015, 80, 5894-5899.


A simple protocol for the deprotection of 1,3-dithianes and 1,3-dithiolanes showed tolerance for a number of phenol and amino protecting groups using 30% aqueous hydrogen peroxide activated by iodine catalyst (5 mol%) in water in the presence of sodium dodecyl sulfate (SDS) under essentially neutral conditions without any detectable overoxidation.
N. G. Ganguly, S. K. Barik, Synthesis, 2009, 1393-1399.

An efficient and convenient procedure has been developed for the hydrolysis of thioacetals/thioketals to the corresponding carbonyl compounds in excellent yields with o-iodoxybenzoic acid (IBX) in presence of β-cyclodextrin (β-CD) in water under neutral conditions at room temperature.
N. S. Krishnaveni, K. Surendra, Y. V. D. Nageswar, K. R. Rao, Synthesis, 2003, 2295-2297.

An efficient, mild and chemoselective method for the deprotection of S,S-acetals to the corresponding carbonyl compounds using silicasulfuric acid/NaNO3 is reported.
A. R. Hajipour, A. Zarei, L. Khazdooz, A. E. Ruoho, Synthesis, 2006, 1480-1484.

A number of new reactions of IBX with heteroatom-containing substrates were discovered and their utility was demonstrated. IBX was used for the generation of imines from secondary amines in notably high yields, for the oxidative aromatization of nitrogen heterocycles and for the cleavage of dithianes.
K. C. Nicolaou, C. J. N. Mathison, T. Montagnon, Angew. Chem. Int. Ed., 2003, 42, 4077-4082.

A new and efficient method for the cleavage of the PMP, THP and 1,3-dithiane protecting groups with Selectfluor™ has been developed.
J. Liu, C.-H. Wong, Tetrahedron Lett., 2002, 43, 4037-4039.

Oxidative deprotection of several dithiane-containing alkaloids in the presence of bis(trifluoroacetoxy)iodobenzene and a nonchromatic purification cleanly generates the corresponding ketoamines. The described procedure is ideal for labile alkaloids.
F. F. Fleming, L. Funk, R. Altundas, Y. Tu, J. Org. Chem., 2001, 66, 6502 - 6504.

Conversion of Dithianes to Other Functional Groups

Easily prepared 2-alkyl-1,3-dithiane derivatives were reacted with BrF3 to form the corresponding 1,1-difluoromethyl alkanes in good yield. The reaction proceeds well with primary alkyl halides. The limiting step for secondary alkyl halides is the relatively low yield of the dithiane preparation.
R. Sasson, A. Hagooly, S. Rozen, Org. Lett., 2003, 5, 3635-3641.

A wide variety of functionalized orthoesters can be prepared under mild and green electrochemical conditions from easily accessible dithiane derivatives.
A. D. Garcia, M. C. Leech, A. Petti, C. Denis, I. C. A. Goodall, A. P. Dobbs, K. Lam, Org. Lett., 2020, 22, 3875-3878.

Dithianes in Multi-step Syntheses

Corey-Seebach Reaction

A linchpin coupling protocol is based on anion relay chemistry (ARC). The addition of an anion to an epoxide, bearing on a distal carbon a trialkyl silyl group and an anion stabilizing group furnishes upon epoxide ring opening an oxyanion. Addition of HMPA triggers a solvent controlled 1,4-Brook rearrangement leading to a new distal anion, which reacts with various electrophiles.
A. B. Smtih, III, M. Xiang, J. Am. Chem. Soc., 2006, 128, 66-67.

Arenesulfonates of primary alcohols react smoothly with lithio derivatives of 1,3-dithiane and 2-phenyl-1,3-dithiane at room temperature to give 2-alkyl derivatives in high yields.
D. Seebach, E.-M. Wilka, Synlett, 1976, 476-477.

While 3,4;5,6-di-O-isopropylidene-N-phthaloyl-D-glucosamine propane-1,3-diyl dithioacetal underwent fast β-elimination, the corresponding N-acetyl derivative was easily deprotonated with butyllithium to form the dilithiated intermediate. Stoichiometry and temperature were crucial factors for selective C-C coupling with various electrophiles.
Y.-L. Chen, R. Leguijt, H. Redlich, R. Fröhlich, Synthesis, 2006, 4212-4218.

Multicomponent Linchpin Coupling of Silyl Dithianes Employing an N-Ts Aziridine as the Second Electrophile: Synthesis of (-)-Indolizidine 223AB
A. B. Smith, D.-S. Kim, Org. Lett., 2004, 6, 1493-1495. DOI: 10.1021/jo035391p (free Supporting Information)


The role of 1,3-dithianes in natural product synthesis
Miguel Yus, Carmen Nájera and Francisco Foubelo, Tetrahedron, 2003, 59, 6147-6212. DOI: 10.1016/S0040-4020(03)00955-4