Allylic Substitution, Allylation
The cross-coupling reaction of aryl and vinyl boronic acids and allylic alcohols proceeded smoothly in toluene or dioxane in the presence of a (triphenyl phosphite)palladium catalyst to give the corresponding allylbenzene derivatives and 1,4-dienes. Neither cocatalysts for promoting C-O bond cleavage of allylic alcohols nor bases for activation of organoboron reagents are required.
Y. Kayaki, T. Koda, T. Ikariya, Eur. J. Org. Chem., 2004, 4989-4993.
Palladium-catalyzed allyl cross-coupling reaction of allylic acetates with various boronic acids gave allyl arene derivatives in good yields at room temperature in the presence of a catalytic amount of Pd(OAc)2 with phosphine-free hydrazone as ligand.
T. Mino, K. Kajiwara, Y. Shirae, M. Sakamoto, T. Fujita, Synlett, 2008, 2711-2715.
A cross-coupling reaction between aryl- and vinylboronic acids and various allylic bromides proceeded without the use of a transition-metal catalyst to give the corresponding allylated products in good yields. The use of an inorganic base and a small amount of water is crucial in obtaining good performance in the present transition-metal-free reaction.
M. Ueda, K. Nishimura, R. Kashima, I. Ryu, Synlett, 2012, 1085-1089.
The Pd(0)-catalyzed allylic cross-coupling of homoallylic tosylate substrates using boronic acids and pinacol esters uses 2-(4,5-dihydro-2-oxazolyl)quinoline (quinox) as a ligand and is performed at ambient temperature. The scope of the reaction is broad in terms of both the boronate and the tosylate, that includes secondary tosylates.
B. J. Stokes, S. M. Opra, M. S. Sigman, J. Am. Chem. Soc., 2012, 134, 11408-11411.
A copper-catalyzed SN2'-selective arylation of various allylic chlorides with arylboronic esters in the presence of a wide range of functional groups leads to branched products in high yield. A mechanism is proposed on the basis of the results of stoichiometric experiments and the isolation of the proposed intermediate.
A. M. Whittaker, R. P. Rucker, G. Lalic, Org. Lett., 2010, 12, 3216-3218.
Allyl-aryl coupling between allylic acetates and arylboronic acids took place in the presence of catalytic amounts of Pd(OAc)2, 1,10-phenanthroline, and AgSbF6 with high γ-selectivity and E:Z-selectivity. The reaction of an optically active allylic acetate with an α-stereogenic center proceeded with excellent α-to-γ chirality transfer.
H. Ohmiya, Y. Makida, T. Tanaka, M. Sawamura, J. Am. Chem. Soc., 2008, 130, 17276-17277.
In situ generated palladium(0) nanoparticles catalyze an efficient cross-coupling of allyl acetates with aryl and vinyl siloxanes. The reactions are stereoselective, and linear (E)-coupling products are obtained both from cis and trans allyl acetates. The coupling with vinyl siloxanes provides a novel protocol for the synthesis of 1,4-pentadienes.
R. Dey, K. Chattopadhyay, B. C. Ranu, J. Org. Chem., 2008, 73, 9461-9464.
A room-temperature Ni-catalyzed reductive coupling of aryl bromides with secondary alkyl bromides provides products in good to excellent yields. Slight modification of this protocol allows efficient coupling of activated aryl chlorides with cyclohexyl bromide and aryl bromides with allylic acetate.
S. Wang, Q. Qian, H. Gong, Org. Lett., 2012, 14, 3352-3355.
An efficient Hiyama coupling reaction between benzylic halides and aryltrialkoxysilanes using Pd nanoparticles allows the synthesis of a diverse range of diarylmethanes which are ubiquitous units of natural products and pharmaceuticals.
D. Srimani, A. Bej, A. Sarkar, J. Org. Chem., 2010, 75, 4296-4299.
Coupling of sterically hindered aryl and activated alkyl chlorides bearing β-hydrogens has been successfully achieved by using N-heterocyclic carbene (NHC)Pd-carboxylate complexes as catalysts.
R. Singh, M. S. Viciu, N. Kramareva, O. Navarro, S. P. Nolan, Org. Lett., 2005, 7, 1829-1832.
A γ-selective, palladium-catalyzed cross-coupling of sodium (Z)-2-butenyldiethylsilanolate provides high yields and site selectivity with electron-rich, electron-poor, sterically hindered, and heteroaromatic bromides. The use of a configurationally homogeneous (Z)-silanolate, nontransferable ethyl groups, and a sterically bulky trialkylphosphonium tetrafluoroborate salt are critical to the success of the method.
S. E. Denmark, N. S. Werner, Org. Lett., 2011, 13, 4596-4599.
Functionalized diarylzinc reagents react readily with allylic chlorides or phosphates in the presence of Co(acac)2 as catalyst to give the SN2 products in high yields and with retention of the double-bond configuration. Functionalities such as ester, ketone, or cyano are tolerated.
G. Dunet, P. Knochel, Synlett, 2007, 1383-1386.
The use of Zn powder in the presence of LiCl in THF allows a simple, high-yielding preparation of a broad range of functionalized aryl- and heteroarylzinc reagents. The synthesis of alkylzinc reagents was performed from inexpensive alkyl bromides.
A. Krasovski, V. Malakhov, A. Gavryushin, P. Knochel, Angew. Chem. Int. Ed., 2006, 45, 6040-6044.
Generation of a π-allyl Pd species directly from a 1,3-diene via a Pd-catalyzed aerobic alcohol oxidation enables a palladium-catalyzed reductive cross-coupling of 1,3-dienes with boronic esters. Both the scope of the process and the origin of a highly selective 1,2-addition are discussed.
L. Liao, M. S. Sigman, J. Am. Chem. Soc., 2010, 132, 10209-10211.
The palladium-catalyzed reaction of allyl acetates with aryl- and vinyltin reagents gave good yields of cross-coupled products. The reaction was mild and tolerant of functionality (-CO2R, -OH, -OSiR3, -OMe) in the tin reagent. Inversion of stereochemistry at the acetate center was observed, with retention of the geometry of the olefin of the allyl group and with exclusive coupling at the primary position. Retention of geometry of the olefin in the vinyltin reagents was also observed.
L. Del Valle, J. K. Stille, L. S. Hegedus, J. Org. Chem, 1990, 55, 3019-3023.
Palladium-catalyzed coupling reactions of functionalized allylboronic acids with various iodobenzenes under standard Suzuki-Miyaura coupling conditions afforded selectively the branched allylic products in high to excellent yields.
S. Sebelius, V. J. Olsson, O. A. Wallner, K J. Szabó, J. Am. Chem. Soc., 2006, 128, 8150-8151.
Sodium allyldimethylsilanolates and 2-butenyldimethylsilanolates undergo cross-coupling with a wide variety of aryl bromides to afford allylated and crotylated arenes. Reactions of allyldimethylsilanolate take place in DME with allylpalladium chloride dimer whereas 2-butenyldimethylsilanolate delivered branched products in toluene in the presence of Pd(dba)2 and norbornadiene as ligand.
S. E. Denmark, N. S. Werner, J. Am. Chem. Soc., 2008, 130, 16382-16393.
Silylated cyanohydrins of iodo-substituted aryl, heteroaryl, or cycloalkenyl ketones undergo an I/Mg-exchange using i-PrMgCl·LiCl. After subsequent reactions with electrophiles, a facile deprotection produces polyfunctional ketones in good overall yiels. An extension to aromatic iodoaldehydes is described.
C.-Y. Liu, H. Ren, P. Knochel, Org. Lett., 2006, 8, 617-629.
Treatment of fluorapatite with an aqueous solution of RhCl3 resulted in rhodium-exchanged fluorapatite catalyst (RhFAP), which successfully promoted cross coupling of Baylis-Hillman adducts with a variety of arylboronic acids to yield trisubstituted olefins in a highly stereoselective manner. RhFAP was recovered quantitatively by simple filtration and reused with almost consistent activity.
M. L. Kantam, K. B. S. Kumar, B. Sreedhar, J. Org. Chem., 2008, 73, 320-322.
A highly enantioselective Rh-catalyzed asymmetric allylic substitution allows the desymmetrization of meso cyclopent-2-ene-1,4-diethyl dicarbonates. Depending on the ligand, each of two regioisomeric products can be obtained in good yield and excellent enantioselectivity. Whereas bisphosphine P-Phos ligands form trans-1,2-arylcyclopentenols, Segphos ligands lead predominantly to trans-1,4-arylcyclopentenols.
F. Menard, D. Perez, D. S. Roman, T. M. Chapman, M. Lautens, J. Org. Chem., 2010, 75, 4056-4068.