A breakthrough synthetic process for β-carotene has been unveiled, promising significantly higher yields and reduced production costs compared to established methods. β-carotene, a vital non-vitamin A precursor carotenoid, is renowned for its potent antioxidant properties and crucial role in human health. It is instrumental in preventing degenerative diseases, supporting cardiovascular health, and potentially reducing cancer risks. However, traditional industrial synthesis routes, often relying on costly vitamin A derivatives or generating problematic waste like triphenylphosphine oxide, struggled with low yields (around 60%) and complex, expensive purification steps.

The innovative method focuses on optimizing the critical Wittig-Horner reaction step. It utilizes a specifically formulated reaction-promoting solvent system composed of 5-10 vol% organic secondary amine (e.g., diethylamine or methyl ethyl amine), 10-15 vol% C5-C8 alkane (e.g., hexane or heptane), and 75-85 vol% methanol or ethanol. This unique blend enhances the solubility of the base catalyst, mitigating side reactions and driving the desired reaction pathway.

Key reactants, 2,4-pentadienal C15 phosphonate ester and 2,7-dimethyl-2,4,6-octatriene-1,8-dial, are dissolved in this solvent mixture in a precise molar ratio between 2.0:1 and 2.2:1. Crucially, the reaction is performed under tightly controlled low temperatures (-10°C to 0°C). A basic compound, such as sodium methoxide, sodium tert-butoxide, sodium hydroxide, or sodium hydride, is added in portions to prevent runaway temperature increases. The reaction mixture is maintained for 4-6 hours to ensure complete conversion.

This optimized approach yields a notable improvement. Laboratory trials demonstrated β-carotene recovery rates up to 85%, substantially exceeding common industrial values. Furthermore, the process utilizes readily available and lower-cost raw materials compared to vitamin A routes. Post-reaction workup is greatly simplified; the isolation primarily involves straightforward filtration and drying. The solvent mix is also designed for efficient recovery and reuse, enhancing cost-effectiveness and reducing environmental impact.

Detailed examples illustrate the process efficacy. In one trial, dissolving C15 phosphonate ester (35.8g, 95%, 0.1 mol) and C10 dialdehyde (8.2g, 0.05 mol) in a solvent mixture of diethylamine, hexane, and methanol (5mL:10mL:85mL) at 0°C, followed by gradual addition of sodium tert-butoxide (11.5g, 0.12 mol) in batches over 30 minutes resulted in a reaction yield of approximately 85% after 5 hours. Other trials using methyl ethyl amine and differing bases like sodium methoxide or NaOH yielded 74% and 60% respectively under slightly varied conditions, showcasing the importance of optimized temperature and base selection. Crucially, the reaction-promoting solvent system proved essential in maximizing base solubility and minimizing unwanted side products, directly underpinning the high yield.

Characterization, including ¹H-NMR spectroscopy in CDCl₃ (δ 6.67-6.24 m, 6H; δ 6.15-6.11 m, 6H; δ 2.02 s, 4H; δ 1.97 s, 12H; δ 1.72 s, 6H; δ 1.46-1.47 d, 4H; δ 1.03 s, 12H), confirmed the identity and high purity of the synthesized β-carotene. With its combination of significantly enhanced yield, simplified purification avoiding problematic byproducts, lower raw material costs, recoverable solvents, and operational feasibility, this new synthetic pathway marks a substantial advancement for the efficient and cost-effective industrial production of this essential nutrient and antioxidant.