Rhodium-catalyzed Addition of Aryl- and Alkenylsilanediols to Aldehydes

Abstract

Arylation and alkenylation of aromatic aldehydes with silanediols is shown to proceed by use of a catalytic amount of rhodium complex. Treatment of ethyl(4-methoxyphenyl)silanediol with benzaldehyde in the presence of 3 mol% of [Rh(OH)(cod)] 2 affords 4-methoxyphenyl(phenyl)methanol in 59% yield after stirring at 70°C for 24 hours. On the other hand, diarylketone was also obtained at elevated temperature via b-hydride elimination from intermediary rhodium alkoxide.Nucleophilic addition of aryl-and alkenyl-metal reagents to carbonyl compounds has been a fundamental reaction in organic synthesis. By contrast to the highly reactive organometallic nucleophilic reagents such as lithium or magnesium, use of an organosilicon reagent has rarely been studied so far. 1-3 We have recently been studying the synthetic application of silanols, a new class of organosilicon reagent bearing hydroxy groups on the silicon atom, and revealed that the carbon-silicon bond of silanols successfully affect several carbon-carbon bond-forming reactions by the catalysis of a transition metal complexes. 4 Indeed, we reported that organosilicon reagents bearing hydroxy groups on the silicon atom affect Mizoroki-Heck (MH) type reaction and conjugate addition to a,b-unsaturated carbonyl compounds in the presence of a catalytic amount of a rhodium complex. 5 Hence, we envisaged the addition of such aryl-and alkenylsilanediols to aldehydes with the rhodium catalyst.The reaction of ethyl(4-methoxyphenyl)silanediol (1) with benzaldehyde (2a) was carried out in the presence of 3 mol% of [Rh(OH)(cod)] 2 in THF at 70 °C, which conditions were similar to those for the MH-type reaction of a,b-unsaturated carbonyl compounds. 5 The corresponding secondary alcohol was obtained in 59% yield after stirring for 24 hours as shown in the Equation.The table summarizes the results on the rhodium-catalyzed reactions of several aldehydes and silanediols. The reaction with twice molar amounts of silanediol to aldehyde was found to be optimum. A cationic rhodium complex, [Rh(cod)(CH 3 CN) 2 ]BF 4 similarly catalyzed the addition reaction. However, addition of several phosphines as a ligand of the rhodium complex inhibited the reaction. A polar and non-aqueous solvent such as THF, DME, or 1,4-dioxane was found to be excellent, while use of water as co-solvent resulted in no reaction by contrast to the related reaction with boronic acid. 3a-c A protic solvent, MeOH was also found to be uneffective. Aromatic aldehydes bearing an electron-donating or -withdrawing group 2b-e both afforded the corresponding secondary alcohols in better yields than benzaldehyde (2a). The reaction of ethyl(4-methoxyphenyl)silanediol (1) with various aromatic aldehydes also resulted in giving good yields. In addition to arylsilanediols, the use of alkenylsilanediol 4 afforded the corresponding allylic alcohol in 79% yield. On the other hand, the reaction with aliphatic aldehydes (2h) was found to be unsuccessful.Oi and Inoue recently reported that aryldifluorosilanes also reacted with aldehyd...

Nucleophilic arylation with tetraarylphosphonium salts

“…However, this approach often suffers from narrow substrate scope, or the high moisture sensitivity and the strong basicity of the reagents. Transition-metal-catalysed arylation of carbonyl or imino groups with aryl halides 12 13 , arylboronic acid derivatives 14 15 16 17 18 19 20 or other reactive reagents 21 22 23 24 25 showed good functional group tolerance under mild reaction conditions. However, the high cost of noble transition metal complexes and possible contamination of the end products by trace amounts of heavy metals probably limit the wide application of this approach in industrial and pharmaceutical processes.…”

Iron‐Catalysed Chemo‐, Regio‐, and Stereoselective Hydrosilylation of Alkenes and Alkynes using a Bench‐Stable Iron(II) Pre‐Catalyst

“…Alkylsilanols have numerous applications in materials chemistry, [6,31] and vinylsilanol products, such as 14b, can be used as substrates in cross-coupling, [32] Mizoroki-Heck, [33] and carbonyl addition reactions. [34] A large body of work has focussed on the development and mechanistic understanding of polymerisation reactions catalysed by iron bisA C H T U N G T R E N N U N G (imino)pyridine complexes. [35] Chirik has also identified and characterised iron(II) dialkyl [5d,12] and iron(0) bis(dinitrogen) and bisA C H T U N G T R E N N U N G (silane) complexes [11] which are effective precatalysts for hydrosilylation, however the in situ observation of the true catalytic species has proved chalScheme 1.…”

Addition reaction of arylboronic acids to aldehydes and α,β-unsaturated carbonyl compounds catalyzed by conventional palladium complexes in the presence of chloroform

“…a,b-Unsaturated carbonyl ester and nitrile were also arylated to give the 1,4-adduct in good yield accompanied with Heck-type product in low yield. Addition of water to the reaction improved the ratio of 1,4-adduct/Hecktype product (Table 4, entries [17][18][19][20][21]. Table 3 Survey of Pd catalysts on 1,4-addition reaction of phenylboronic acid to 2-cyclohexenone.…”

“…9, 110.5, 120.6, 126.3, 126.9, 127.6, 127.9, 128.5, 131.8, 143.1, 156.4. 4.14. Ethyl mandelate (3ak) 1 H NMR (CDCl 3 ): d 1.19 (t, J = 7.2 Hz, 3H, -OCH 2 CH 3 ), 3.61 (brs, 1H, -OH), 4.08-4.28 (m, 2H, -OCH 2 CH 3 ), 5.13 (s, 1H, -CHOH), 7.26-7.42 (m, 5H, -Ar); 13 C NMR (75 MHz) d 14.0,62.1,126.3,128.1,128.3,138.2,methanol (3bf) [21] 1 H NMR (CDCl 3 , 300 MHz) d 2.46 (s, 1H, -OH), 3.79 (s, 3H, -OCH 3 ), 5.94 (s, 1H, -CHOH), 6.86 (d, J = 8.7, 2H, -Ar), 7. 25-7.49 (m, 5H, -Ar), 7.77-7.89 (m, 4H, -Ar); 13 C NMR (75 MHz) d 55.…”