Solvent free Cannizzaro reaction applying grindstone technique

1 Introduction

The redox disproportionation of non-enolizable aldehydes to carboxylic acids and alcohols was conducted in potassium carbonate by Cannizzaro in 1853, known as Cannizzaro reaction (Cannizzaro, 1853; Geissman, 1944; List and Limpricht, 1854; Phonchaiya et al., 2009). The Cannizzaro reaction is one of the oldest and interesting organic reactions that depends on solvent and requires heating in the presence of base, usually concentrated aqueous base. Even though Cannizzaro reaction is the oldest and uses the known reaction method, it continues to attract the attention of chemists due to its interesting synthetic and mechanistic challenges (Abaee et al., 2005; Curini et al., 2005; Vida et al., 2005). The development of the Cannizzaro reaction has been made in the past several years. Strong bases, such as NaOH, KOH, Ba(OH)₂ and LiOH (Cannizzaro, 1853; Geissman, 1944; List and Limpricht, 1854; Phonchaiya et al., 2009; Antonio et al., 2008), LiBr with Et₃N (Mojtahedi et al., 2007), cation templates (Vida et al., 2005) with NaOH, solvent-free conditions (Yoshizawa et al., 2001) with KOH at 100 °C, ruthenium-catalyzed transfer hydrogenation (Vida et al., 2005; Kim et al., 2003), in the presence of KOH, NaOH, microwave irradiation (Sharifi et al., 1999; Varma et al., 1998) with A1₂O₃(basic), NaOH, and Ba(OH)₂, ultrasound mediation (Entezari and Shameli, 2000) in KOH have been introduced for the methodology development of the reaction. Lewis acid (Russell et al., 2000; Yang et al., 2005) catalysts such as, Cu(OTf)₂ and Ln(OH)₃, Organo-base (Basavaiah et al., 2006), magnesium bromide ethyl etherate and triethylamine in room-temperature (Abaee et al., 2005), aqueous solid–liquid biphasic reaction in presence of cyclodextrins (Canipelle et al., 2011), solid-supported reagents (Reddy et al., 2002) with KF-Al₂O₃, gas-phase process (Sheldon et al., 1997), photo induction (Kagan, 1996) and chiral Lewis acid (Ishihara et al., 2008) have also been applied for the development of the methodology. In addition, crossed Cannizzaro version (Curini et al., 2005) of the reaction with Yb(OTf)₃, intramolecular Cannizzaro reaction in the presence of tetraethyl ammonium hydroxide have (Akhigbe et al., 2009) recently been used. Nevertheless, up to this point the development of procedures for the Cannizzaro reaction relied on the use of strong base, solvent and hazard workup condition, which led continuing interests to develop an efficient procedure and/or catalyst. We herein describe a simple, efficient, inexpensive, time saving, solvent free procedure for the Cannizzaro reaction applying grindstone technique in the presence of solid sodium hydroxide.

2 Experimental

3 Results and discussion

In this communication, we have disclosed the conversation of aryl aldehydes (1) to aryl carboxylic acid (2) and aryl alcohol (3). Reaction proceeds without any solvents and grindstone technique was used for the redox disproportion of various aryl aldehydes (1) in the presence of sodium hydroxide pellets (Scheme 1).

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Scheme 1

Cannizzaro reaction of various aryl aldehydes using solid NaOH pellets.

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While a mixture of aryl aldehyde (1) and one equivalent of solid NaOH plates were ground for approximately 10 min. and under the hood, the reaction proceeds exothermically (indicated by rise in temperature of 25–100 °C), the whole mass was then poured into ice cold water, acidified with 2 M HCl and solid precipitate was collected as analytical pure aryl acid. Extraction of water portion with organic solvent gave aryl alcohol, herein, we have shown the data only for the isolation of acid and it is summarized in Table 1.

Table 1 Cannizzaro reaction of aryl aldehydes in the presence of NaOH applying grindstone technique.^a

Entry	Products		Con.c/Yd (%)	Mp (°C) [Lit. mp (°C)] of acids
	Acid	Alcoholb
			100/96	124[121] Gedye et al. (1988)
			100/98	139[139] Clarke and Taylor (1943)
			100/98	124[122] Wolfgang et al. (2002)
			98 / 96	154[153] Baelen and Maes (2008)
			99/97	105[105] Morimoto and Kakiuchi (2004) and Cacchi et al. (2007)
			98/95	152[152] Yang et al. (2004)
			98/94	242[240] Yang et al. (2004)
			97/95	185[184] Yang et al. (2004)
			98/96	183[179] Wolfgang et al. (2002)
			100/99	161[159] Gilman et al. (1943)

a Aldehyde and solid NaOH (1 equiv.) were ground for approximately 10 min.

b Alcohols were not purified except for 3j.

c Conversion of aldehydes.

d Isolated yields.

However, for 1-Naphthanaldehyde, we have isolated the 1-Naphthoic ethanol (3j) (Ragnarsson et al., 2002) as well as 1-Naphthoic acid (2j). The procedure does not employ any halogenated solvents, additional additives, and/or catalysts, which are important from the economical and environmental point of view. In addition, formation of side products that are normally observed under other conditions was not detected. For all the aldehydes used, the conversion rate was almost 100% (no aldehyde was present based on TLC development and NMR experiment). It should be noted that halogen/methoxy substituted at 4-position of aldehydes gives lower yields.

4 Conclusion

In conclusion, a simple and efficient procedure for the Cannizzaro reaction was established. This present method is superior since it is eco-friendly, advantageous over previously described methods in yield, requires no special apparatus, there is simplicity of operation, and is non-hazardous, simple and convenient.