Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Magdalena Urbala

doi:10.3390/catal11121559

Abstract

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Highlights

Today, the multifunctional organic intermediates used in general organic synthesis as well as in industrial high functionality required applications are preferred
The highly selective mono-O-allylation reaction of symmetric BDO is difficult to perform due to the presence of two primary, terminal, and chemically equivalent hydroxyl groups in the diol molecule
Butan-1,4-diol, allyl chloride, NaOH pellets, NaCl, cyclohexane, toluene, anhydrous magnesium sulfate and PT catalysts such as tetramethylammonium bromide (Me4N+Br−), tetra-n-butylammonium bromide (Bu4N+Br−), methyltrioctylammonium bromide (Bu4N+Br−), dodecyltrimethlammonium bromide (Me3DoN+Br−), tetraethylammonium chloride (Et4N+Cl−), trimethylphenylammonium chloride (Me3PhN+Cl−), methyltrioctylammonium chloride (MeOc3N+Cl−), dimethyldioctadecyl ammonium chloride (Me2(R)2N+Cl−, where R is the mixture of homologs with a chain length of C16–C18, Arquad® 2HT), allyl alcohol, diallyl ether and cyclohexanone analytical standard were purchased at Fluka, Merck, Aldrich or POCh Gliwice and were used as supplied

Summary

Introduction

The multifunctional organic intermediates used in general organic synthesis as well as in industrial high functionality required applications are preferred. Besides simple low-molecular-weight compounds such as diallyl ether or simple allyl alkyl ethers, polyallyl alkyl ethers with additional functional groups constitute one of the valuable chemicals in many industries. They are especially used in the free radical or cationic photocuring production of advanced hybrid polymer systems, mainly as monomers, crosslinkers, modifiers, or reactive diluents [3,4]. Wide ranging transformations of allyloxyalcohols open up pathways for one-step synthesis of large variety hybrid systems, fundamental for environmentally friendly industrial applications (Scheme 1)

Methods

Results

Conclusion