Diethylaminosulfur trifluoride

I. Basic Information Table

II. Properties

Physical Properties

Diethylaminosulfur trifluoride (DAST) is a pale yellow to brownish-yellow transparent liquid at room temperature, with a density of approximately 1.22 g/mL (25°C), boiling point of 30–32°C/3 mmHg, normal pressure boiling point of approximately 163.7°C, flash point of 23°C (closed cup), and refractive index of 1.41–1.416. It is soluble in most non-polar organic solvents such as dichloromethane (CH₂Cl₂), chloroform (CHCl₃), and carbon tetrachloride (CCl₄).

Chemical Properties

DAST is a nucleophilic fluorinating reagent and the most widely used member of the (dialkylamino)sulfur trifluoride family. Its core chemical characteristics include:

Fluorinating Capability: Efficiently converts alcohol hydroxyl groups into fluoroalkanes (both primary and secondary alcohols), aldehydes and ketones into gem-difluorides, acyl chlorides into acyl fluorides, and sulfoxides into α-fluorothioethers.

Hydrolytic Sensitivity: Reacts violently with water, decomposing to generate hydrogen fluoride (HF) and the corresponding amine products. Therefore, it must be handled and stored under strictly anhydrous conditions.

Thermal Instability: Relatively stable under normal temperature and pressure, but pure product may explode when heated above 40–50°C, and decomposes above 90°C. Decomposition products include SF₄ and (Et₂N)₂SF₂, which are highly corrosive and can etch glassware.

III. Applications

DAST is one of the most core fluorinating reagents in organic synthesis and pharmaceutical R&D, with an extremely broad range of applications.

In terms of alcohol fluorination, DAST can efficiently convert the hydroxyl groups of primary and secondary alcohols into the corresponding monofluoroalkanes under mild reaction conditions with high chemoselectivity. It is one of the most commonly used methods for alcohol hydroxyl fluorination in both laboratory and industrial production.

In terms of carbonyl fluorination, DAST can directly convert aldehydes into gem-difluorides at low temperature or room temperature. For ketone substrates, efficient gem-difluorination can also be achieved by appropriately increasing the temperature or extending the reaction time. In addition, DAST can react with acyl chlorides to generate the corresponding acyl fluorides, and with sulfoxides to obtain α-fluorothioethers, which can be further oxidized to prepare α-fluorosulfoxides.

In the field of pharmaceutical and heterocyclic synthesis, DAST is a key fluorinating agent in the synthesis of anticancer drugs, antiviral drugs, and various fluorinated drug molecules. It can also catalyze the Beckmann rearrangement and cyclization of oxime compounds for the synthesis of polysubstituted 2-oxazolines, benzimidazoles, benzopyrazoles, and other nitrogen-containing heterocyclic compounds. In carbohydrate chemistry, DAST enables selective fluorination modification of sugar molecules. Recent studies have also found that DAST can serve as a base-free amidation reagent for efficient coupling of carboxylic acids with amines, further expanding its application boundaries in organic synthesis.

IV. Preparation Methods

Laboratory Preparation

The classic synthetic route for DAST was reported by Middleton in 1975. The core reaction is the fluorination of N,N-diethylaminotrimethylsilane with sulfur tetrafluoride (SF₄):

Et2​NSiMe3​+SF4​→Et2​NSF3​+Me3​SiF

After the reaction, the byproduct trimethylfluorosilane (Me₃SiF) and excess SF₄ are removed by vacuum distillation to obtain crude DAST. Further rectification yields high-purity product.

Industrial Preparation

Given the heat-sensitive and explosive nature of DAST, industrial production adopts a continuous, modular production system. The main equipment includes:

High-level reactor (connected to SF₄ storage tank and adsorption tower)

Reaction kettle (with stirring and liquid nitrogen cooling device)

Concentration kettle (product outlet)

Solvent recovery kettle (connected to oil pump for solvent recovery)

This system achieves independent operation of each unit without mutual interference through a specific height difference design. It enables safe, continuous production from kilogram to ton scale even with relatively low raw material purity requirements (≥82%).

V. Safety Information

GHS Hazard Classification

DAST is classified as a flammable liquid (Category 3) with acute toxicity (oral, inhalation, dermal, Category 4). It is extremely corrosive to skin and eyes (skin corrosion/irritation Category 1B, serious eye damage Category 1) and is classified as a suspected carcinogen (Category 2).

Main Hazard Statements

H226: Flammable liquid and vapor

H314: Causes severe skin burns and eye damage

H331: Toxic if inhaled

H351: Suspected of causing cancer

Handling and Storage

DAST must be handled in a fume hood. Operators must wear chemical-resistant gloves (nitrile or neoprene recommended), goggles or face shields, and protective clothing. The operation area should be kept away from heat sources, sparks, and open flames. Contact with moisture is strictly prohibited. For storage, keep in a sealed container at 2–8°C under low temperature, with nitrogen protection, and away from incompatible substances such as water, alcohols, strong oxidizers, strong acids, strong bases, and glass.

First Aid Measures

Skin Contact: Immediately remove contaminated clothing, rinse with plenty of water, and apply 2.5% calcium gluconate gel. In severe cases, subcutaneous injection of calcium gluconate is required.

Eye Contact: Immediately rinse with plenty of water for at least 15 minutes and seek emergency medical attention.

Inhalation: Quickly move to fresh air, maintain unobstructed breathing, perform artificial respiration if necessary, and seek medical attention immediately.

Firefighting and Transportation

Use dry chemical or carbon dioxide fire extinguishers for firefighting. Water or foam is strictly prohibited as it may intensify the reaction. For transportation, the UN number is UN 2920 (Class 8 Corrosive Substance) or UN 3225 (Class 4.1 Self-Reactive Substance Type D), Packing Group I, with the proper shipping name “SELF-REACTIVE LIQUID TYPE D (DIETHYLAMINOSULFUR TRIFLUORIDE)”.

VI. Our Production Advantages and Capacity

Core Advantages

Large-Scale Continuous Production: We adopt a self-developed modular continuous production system, breaking through the safety bottlenecks of traditional batch processes, achieving stable supply from kilogram to ton scale.

Stable and Controllable Quality: Full-process inert gas protection with online monitoring at key stages. Product purity is stably maintained at ≥95% (GC), with minimal batch-to-batch variation, meeting the high standards of pharmaceutical intermediates and R&D-grade requirements.

Comprehensive Safety System: In response to the heat-sensitive and explosive characteristics of DAST, we have established a full-chain safety control system from raw material intake, reaction control, concentration and purification to finished product packaging, equipped with liquid nitrogen deep cooling, explosion-proof interlocks, and emergency neutralization devices.

Self-Controllable Supply Chain: Core raw materials such as SF₄ and diethylamino silane derivatives have stable supply channels. The system has strong adaptability to raw material purity (≥82% is sufficient for production), offering significant cost advantages.

Customized Services: We can provide different packaging specifications (1 kg, 25 kg, and ton drums) according to customer needs, along with complete Chinese and English versions of COA, MSDS/SDS, and transport identification reports.

Capacity Guarantee

Annual Capacity: 50 tons/year (expandable according to market demand)

Standing Inventory: Maintains 3–5 tons of finished product safety stock year-round to ensure rapid delivery of spot goods

Delivery Cycle: Regular orders shipped within 3–7 working days; bulk orders can be scheduled through consultation

Packaging Specifications: 1 kg/bottle (fluorinated bottle with inert gas protection), 25 kg/drum, 200 kg/drum