An Et3SiH-promoted diastereoselective reductive aldol reaction has been developed using InBr3 as a catalyst. This three-component reaction afforded only silyl aldolates as products without any side reactions.
I. Shibata, H. Kato, T. Ishida, M. Yasuda, A. Baba, Angew. Chem. Int. Ed., 2004, 43, 711-714.
An efficient methodology for the reductive alkylation of secondary amines with aldehydes and Et3SiH using an iridium complex as a catalyst has been developed. In addition, a cheaper, easy-to-handle, and environmentally friendly reducing reagent such as polymethylhydrosiloxane (PMHS) in place of Et3SiH was also useful.
T. Mizuta, S. Sakaguchi, Y. Ishii, J. Org. Chem., 2005, 70, 2195-2199.
Reductive amination of aldehydes and ketones with the InCl3/Et3SiH/MeOH system is highly chemoselective and can be applied to various cyclic, acyclic, aromatic, and aliphatic amines. Functionalities including ester, hydroxyl, carboxylic acid, and olefin are tolerated.
O.-Y. Lee, K.-L. Law, C.-Y. Ho, D. Yang, J. Org. Chem., 2008, 73, 8829-8837.
A simple iron- and silyl chloride catalyzed reductive etherification enables the preparation of symmetrical and nonsymmetrical ethers from various aldehydes and ketones in the presence of triethylsilane as a reducing agent and catalytic amounts of iron(III) oxo acetate and chloro(trimethyl)silane. The reactions can be carried out at ambient temperatures in ethyl acetate as the solvent.
R. Savela, R. Leino, Synthesis, 2015, 47, 1749-1760.
Facile reductive etherification of carbonyl compounds can be conveniently performed by reaction with triethylsilane and alkoxytrimethylsilane catalyzed by iron(III) chloride. The corresponding alkyl ethers, including benzyl and allyl ethers, of the reduced alcohols were obtained in good to excellent yields under mild reaction conditions.
K. Iwanami, H. Seo, Y. Tobita, T. Oriyama, Synthesis, 2005, 183-186.
A novel one-pot procedure for a directly reductive conversion of esters to the corresponding ethers by Et3SiH in the presence of a catalytic amount of InBr3 is described. This simple catalytic system appeared to be remarkably tolerant to several functional groups.
N. Sakai, T. Moriya, T. Konakahara, J. Org. Chem., 2007, 72, 5920-5922.
Various silyl ethers were readily and efficiently transformed into the corresponding alkyl ethers in high yields by the use of aldehydes combined with triethylsilane in the presence of a catalytic amount of iron(III) chloride.
K. Iwanami, K. Yano, T. Oriyama, Synthesis, 2005, 2669-2672.
A chemoselective activation of a secondary amide with triflic anhydride in the presence of 2-fluoropyridine enables a mild reduction using triethylsilane, a cheap and rather inert reagent. Imines can be isolated after a basic workup or readily transformed to the aldehydes following an acidic workup. The amine moiety can be accessed by addition of Hantzsch ester to the reaction mixture.
G. Pelletier, W. S. Bechara, A. B. Charette, J. Am. Chem. Soc., 2010, 132, 12817-12819.
A one-pot reaction for the transformation of common secondary amides into amines with C-C bond formation consists of in situ amide activation with Tf2O followed by partial reduction and addition of C-nucleophiles. The method is general in scope and allows the use of both hard nucleophiles (RMgX, RLi) and soft nucleophiles, as well as enolates. With soft nucleophiles the presence of ester, cyano, nitro, and tertiary amide groups are tolerated.
P.-Q. Huang, Y.-H. Huang, K.-J. Xiao, Y. Wang, X.-E. Xia, J. Org. Chem., 2015, 80, 2861-2868.
The use of hydrosilanes as reducing agents in the presence of a palladium catalyst enables an efficient synthesis of aldehydes from acid chlorides. A simple mixture of commercially available Pd(dba)2 and Mes3P catalyzed the reduction of various acid chlorides including aliphatic acid chlorides and α,β-unsaturated acid chlorides to the corresponding aldehydes in good to high yields under mild reaction conditions.
T. Fujihara, C. Cong, T. Iwai, J. Terao, Y. Tshuji, Synlett, 2012, 23, 2389-2392.
A palladium-catalyzed reduction of 2-pyridinyl esters using hydrosilanes is applicable to the preparation of aliphatic, aromatic, and α,β-unsaturated aldehydes. Various functional groups, such as fluoro, methoxy, aldehyde, acetal, and ester, are tolerated.
J. Nakanishi, H. Tatamidani, Y. Fukumoto, N. Chatani, Synlett, 2006, 869-872.
A ligandless palladium-catalyzed reductive carbonylation of aryl iodides for the synthesis of aromatic aldehydes proceeded effectively even under ambient temperature and pressure.
W. Han, B. Liu, J. Chen, Q. Zhou, Synlett, 2017, 28, 835-840.
A palladium-catalyzed formylation of aryl halides with isocyanide in the presence of Et3SiH provides important aldehydes in good yield. This reaction offers mild conditions, convenient operation, low toxicity, and wide functional group tolerance.
X. Jiang, J.-M. Wang, Y. Zhang, Z. Chen, Y.-M. Zhu, S.-J. Ji, Org. Lett., 2014, 16, 3492-3495.
Optimizations to generate CuH in situ have led to an efficient and inexpensive hydrosilylation method for dialkyl ketones.
B. H. Lipshutz, C. C. Caires, P. Kuipers, W. Chrisman, Org. Lett., 2003, 5, 3085-3088.
A regioselective reductive ring opening of benzylidene acetals in carbohydrate derivatives using triethylsilane and molecular iodine is fast and compatible with most of the functional groups encountered in oligosaccharide synthesis, and offers excellent yields. The reaction conditions are equally effective in thioglycosides.
R. Panchadhayee, A. K. Misra, Synlett, 2010, 1193-1196.
Aliphatic carboxyl derivatives (acids, acyl chlorides, esters) and aldehydes were efficiently reduced to the methyl group by HSiEt3 in the presence of catalytic amounts of B(C6F5)3. Aromatic carboxylic acids, as well as other carbonyl functional equivalents, underwent smooth partial reduction to the corresponding TES-protected benzylic alcohols in competition with a Friedel-Crafts-like alkylation decreasing the overall selectivity of the reduction process.
V. Gevorgyan, M. Rubin, J.-X. Liu, Y. Yamamoto, J. Org. Chem, 2000, 66, 1672-1675.
Proper solvent selection between Cl(CH2)2Cl and CF3CH2OH was the key to high yields in a deoxygenation of propargyl alcohols in the presence of Et3SiH and H3[PW12O40]ĚnH2O as catalyst. Under similar conditions, the deoxygenation of allyl alcohols proceeded to give thermodynamically stable alkenes with migration of the double bonds in good yields.
M. Egi, T. Kawai, M. Umemura, S. Akai, J. Org. Chem., 2012, 77, 7092-7097.
In situ generation of molecular hydrogen by addition of triethylsilane to palladium on charcoal results in rapid and efficient reduction of multiple bonds, azides, imines, and nitro groups, as well as deprotection of benzyl and allyl groups under mild, neutral conditions.
P. K. Mandal, J. S. McMurray, J. Org. Chem., 2007, 72, 6599-6601.
A new procedure for catalytic reductive coupling of aldehydes and alkynes uses Ni(COD)2 with an imidazolium carbene ligand as the catalyst and triethylsilane as the reducing agent.
G. M. Mahandru, G. Liu, J. Montgomery, J. Am. Chem. Soc., 2004, 126, 3698-3699.
An intermolecular reductive coupling of ynoates and aldehydes in the presence of a silane using catalytic amounts of Ni(COD)2, an N-heterocyclic carbene ligand, and PPh3 delivers invaluable silyl-protected γ-hydroxy-α,β-enoates. This methodology provides a quick entry to many other 1,4-difunctional compounds and oxygen-containing five-membered rings. The intermediacy of metallacycles in the catalytic process has been established.
S. K. Rodrigo, H. Guan, J. Org. Chem., 2012, 77, 8303-8309.
A three-component nickel-catalyzed coupling of enals, alkynes, and silanes forms an enol silane and a trisubstituted alkene with >98:2 stereoselectivity. The reaction tolerates a broad range of functionality including aldehydes, ketones, esters, free hydroxyls, and basic secondary amines.
A. Herath, J. Montgomery, J. Am. Chem. Soc., 2008, 130, 8132-8133.
The use of a catalytic amount of PtCl2 enables the conversion of α-hydroxypropargylsilanes to (Z)-silylenones through a highly selective silicon migration via alkyne activation. The complementary (E)-silylenones are accessed by a regioselective hydrosilylation of the ynone precursor.
D. A. Rooke, E. M. Ferreira, J. Am. Chem. Soc., 2010, 132, 11926-11928.
Aldehyde α-hydroperoxides can be accessed from α-substituted acroleins with triethylsilane and water under Pd/C catalysis and aerobic conditions via a Pd/C-catalyzed conjugate reduction step and a subsequent hydroperoxidation step. Upon reduction, 2,2-disubstituted 1,2-diols are obtained.
S. Tuokko, P. M. Pihko, Synlett, 2016, 27, 1649-1652.
A nickel-catalyzed coupling of enones or enals with alkynes in the presence of silane and titanium alkoxide reductants provides direct access to skipped diene products via a net four-electron reductive coupling and deoxygenation. A new class of well-defined nickel(0) precatalysts bearing an unhindered N-heterocyclic carbene ligand is essential for the efficiency of the transformation.
D. P. Todd, B. B. Thompson, A. J. Nett, J. Montgomery, J. Am. Chem. Soc., 2015, 137, 12788-12791.
Indium hydride (Cl2InH) was generated by the transmetalation of InCl3 with Et3SiH. In the previously reported system (NaBH4-InCl3), the coexistent borane can cause side reactions. The use of Et3SiH instead of NaBH4 affords effective hydroindation of alkynes. N. Hayashi, I. Shibata, A. Baba, Org. Lett., 2004, 6, 4981-4983.
The use of Et3SiH and a catalytic amount of I2 enables transition-metal-free, intramolecular hydroalkoxylation/reduction and hydroamination/reduction of unactivated alkynes at room temperature to provide 2,4- and 2,5-disubstituted pyrrolidines as well as a 2,3-disubstituted tetrahydrofurans with high diastereoselectivity.
S. Fujita, M. Shibuya, Y. Yamamoto, Synthesis, 2017, 49, 4199-4204.
An Al(OTf)3-catalyzed cascade cyclization and ionic hydrogenation reaction of nitrogen substituted ketoamides enables an efficient and versatile synthesis of N-substituted lactams, pyrrolindinones, piperidones, and structurally related heterocycles in good yields.
J. Qi, C. Sun, Y. Tian, X. Wang, G. Li, Q. Xiao, D. Yin, Org. Lett., 2014, 16, 190-192.
Palladium-catalyzed reduction of aromatic nitro groups to amines can be accomplished in high yield, with wide functional group tolerance and short reaction times at r.t. using aqueous potassium fluoride and polymethylhydrosiloxane (PMHS) for aromatic nitro groups. Aliphatic nitro compounds are reduced to the corresponding hydroxylamines using triethylsilane instead of PMHS/KF.
R. J. Rahaim, R. E. Maleczka (Jr.), Org. Lett., 2005, 7, 5087-5090.
The sensitive azidocarbenium ion intermediate can be trapped with various nucleophiles to provide azides in excellent chemoselectivity. The method enables the chemoselective synthesis of primary and secondary benzyl azides from aldehydes in a one-pot reaction.
S. Pramanik, P. Ghorai, Org. Lett., 2014, 16, 2104-2107.
Organic azides are easily and chemoselectively reduced to the corresponding amines by reaction with dichloroindium hydride under very mild conditions. γ-Azidonitriles give pyrrolidin-2-imines in an outstanding cyclization.
L. Benati, G. Bencivenni, R. Leardini, D. Nanni, M. Minozzi, P. Spagnolo, R. Scialpi, G. Zanardi, Org. Lett., 2006, 8, 2499-2502.
Reduction of ethanethiol esters of α-amino acids to α-amino aldehydes by triethylsilane and catalytic palladium-on-carbon is described. α-Amino aldehydes with Boc, Cbz, or Fmoc protection could be obtained without racemization in high yield.
H. Tokuyama, S. Yokoshima, S.-C. Lin, L. Li, T. Fukuyama, Synthesis, 2002, 1121-1123.