Phase-transfer reagents Aliquat

Pt-catalyzed hydration of various aliphatic and aromatic alkynes under phase transfer conditions in (CH2C1)2/H20 in the presence of Aliquat 336 led to either a Markovnikov product, mixtures of two ketones, or ketones with the carbonyl group positioned away from the bulky side.72 In the absence of the phase transfer reagent, Aliquat 336, hardly any reaction took place. Recently, a hydrophobic, low-loading and alkylated polystyrene-supported sulfonic acid (LL-ALPS-SO3H) has also been developed for the hydration of terminal alkynes in pure water, leading to ketones as the product.73 Under microwave irradiation, the hydration of terminal arylalkynes was reported to proceed in superheated water (200°C) without any catalysts.74... 

Potassium acetate, for example, can be readily alkylated by the use of an equivalent amount of an alkylating reagent (for example, an alkyl halide) in the presence of the phase-transfer catalyst Aliquat 336 (10 mol%) (Scheme 4.7) [16]. Yields are always near quantitative within a few minutes of microwave irradiation, irrespective of the chain length and the nature of the leaving group. This procedure has been scaled-up from 50 mmol to 2 mol scale in a large batch reactor [17]. 

Wittig-Horner reaction. The reagent reacts with a wide range of aldehydes, aliphatic, aromatic, and a,P-unsaturated, in the presence of a base to form (E)-a-methyl-a, -unsaturated esters stereoselectively. The reaction can be carried out either with potassium t-butoxide in DMF or with K,COj in QH /HjO and Aliquat 336 as phase-transfer agent. 

CsF added to tetra- -butylammonium bromide or Aliquat 336, the mixture stirred for 5 min, n-octyl bromide added, stirring continued for 5 min, and allowed to react for 40 h - n-octyl fluoride. Y 77%. Work-up is easy and reagents readily available yields are high from satd. chlorides and bromides (incl. benzylic), but aromatic bromides were more resistant. F.e. and with tetra-n-butylammonium fluoride, also from tosyla-tes, and comparison with other heterogeneous methods s. G. Bram et al., Synth. Commun. 18, 1661-7 (1988) review of solid-liq. phase transfer catalysis without solvent s. Bull. Soc. Chim. France 1989, 247-51. 

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