Activation of diphenylsilane in the presence of a catalytic amount of an N-heterocyclic carbene (NHC) enables hydrosilylation of carbonyl derivatives under mild conditions. Presumably, a hypervalent silicon intermediate featuring strong Lewis acid character allows dual activation of both the carbonyl moiety and the hydride at the silicon center. Some interesting selectivities have been encountered.
Q. Zhao, D. P. Curran, M. Malacria, L. Fensterbank, J.-P. Goddard, E. Lacôte, Synlett, 2012, 23, 433-437.
The [RuCl2(p-cymene)]2/Ph2SiH2 catalytic system is very efficient for the reductive amination of aldehydes with anilines to provide secondary amines and tertiary amines in good yields. The method is highly chemoselective and tolerates a wide range of functional groups, such as NO2, CN, CO2Me, F, Cl, Br, OMe, Me, furyl and alkyl.
B. Li, J. Zheng, W. Zeng, Y. Li, L. Chen, Synthesis, 2017, 49, 1349-1355.
An environmentally benign, tin-free radical "on water" addition of alkyl iodides to the C=N bond of hydrazones in the presence of diphenylsilane and triethylborane afforded the corresponding addition products in good yields. The developed protocol can be applied to the synthesis of 3-substituted isoindolinone derivatives.
T. K. Nam, D. O. Jang, J. Org. Chem., 2018, 83, 7373-7379.
A mild, enantioselective hydrosilylation of 3-oxo-3-arylpropionic acid methyl or ethyl esters using axially chiral BINAM N-heterocyclic carbene (NHC)-Rh(III) complexes as catalysts gave 3-hydroxy-3-arylpropionic acid methyl or ethyl esters in good yields with good to excellent enantioselectivities under mild conditions.
Q. Xu, X. Gu, S. Liu, Q. Duo, M. Shi, J. Org. Chem., 2007, 72, 2240-2242.
The combination of an air-stable Ni precatalyst, dimethyl dicarbonate as an activator, and diphenylsilane as reductant enables a direct conversion of carboxylic acids to aldehydes for a wide range of substrates in good yields and with no overreduction to alcohols.
A. V. Iosub, S. Moravčík, C.-K. Wallentin, J. Berman, Org. Lett., 2019, 21, 7804-7808.
3-Methyl-1-phenylphospholane-1-oxide as precatalyst and an organosilane reducing agent are the key components in a Wittig reaction catalytic in phosphine. Various heteroaryl, aryl, and alkyl adehydes could be efficiently converted to the corresponding alkenes in good yield using this precatalyst. The protocol also functions well on larger scale.
C. J. O'Brien, J. L. Tellez, Z. S. Nixon, L. J. Kang, A. L. Carter, S. R. Kunkel, K. C. Przeworski, G. A. Chass, Angew. Chem. Int. Ed., 2008, 48, 6836-6839.
Cu-catalyzed asymmetric conjugate reduction of β-substituted ketones leads to enantiomerically enriched diphenylsilyl enol ethers, which are utilized in a diastereoselective Pd-catalyzed α-arylation of various aryl bromides to yield disubstituted cycloalkanones with excellent levels of enantiomeric and diastereomeric purity. The procedure can be carried out in one-pot.
J. Chae, J. Yun, S. L. Buchwald, Org. Lett., 2004, 6, 4809-4812.
A catalytic anti-Markovnikov hydrobromination of aryl- and alkyl-substituted terminal alkynes affords terminal E-alkenyl bromides in high yield and with excellent regio- and diastereoselectivity. The reaction conditions are compatible with a wide range of functional groups, including esters, nitriles, epoxides, aryl boronic esters, terminal alkenes, silyl ethers, aryl halides, and alkyl halides.
M. R. Uehling, R. P. Rucker, G. Lalic, J. Am. Chem. Soc., 2014, 136, 8799-8803.
Cu(I) catalysis enables an efficient and facile construction of trisubstituted exocyclic alkenes in good yields under mild conditions in the presence of B2pin2. Tetrasubsituted borylated or iodinated alkenes can also be isolated depending on the reaction conditions. A preliminary mechanistic study showed that the reaction undergoes a radical process, where B2pin2 plays an indispensable role.
S. Zhou, F. Yuan, M. Guo, G. Wang, X. Tang, W. Zhao, Org. Lett., 2018, 20, 6710-6714.