CAS 13598-36-2 Phosphonic acid - Analytical Products / Alfa Chemistry

CAT	APS13598362
CAS	13598-36-2
Structure
Synonyms	Phosphonic Acid
IUPAC Name	phosphonic acid
Molecular Weight	82.00
Molecular Formula	H3O3P
Canonical SMILES	OP(=O)O
InChI	InChI=1S/H3O3P/c1-4(2)3/h4H,(H2,1,2,3)

Accurate Mass	81.982
Format	Neat
Shipping	Room Temperature
Storage Conditions	+20°C
Subcategory	Fungicides and metabolites

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Case Study

Phosphorous Acid Used for the Catalytic Alkylation of Phenols with Alkenes under Mild Conditions

Wu, Shaofeng, et al. The Journal of Organic Chemistry 85.22 (2019): 14307-14314.

Phosphorous acid (H₃PO₃) has been demonstrated as an efficient Bronsted acid catalyst for the regioselective alkylation of phenols with alkenes. In this study, H₃PO₃ catalyzes a direct C-H alkylation reaction under relatively mild conditions, affording a practical and scalable method for synthesizing ortho-, meta-, or para-alkylated phenol derivatives with excellent selectivity and high yields.
The optimized procedure involves the reaction of phenol (0.4 mmol) with an alkene (1.2 equiv) in 1,2-dichloroethane (DCE) using 20 mol% of 50% aqueous phosphorous acid. The mixture is heated at 100 °C for 18 hours in a sealed Schlenk tube. After completion, standard workup and silica gel chromatography afford the purified mono-alkylated phenol product.
A key advantage of this H₃PO₃-catalyzed reaction lies in its unique selectivity profile: it effectively suppresses overalkylation and prevents undesired alkylation on simple phenyl rings. Moreover, the protocol shows broad functional group tolerance and can be applied to the late-stage functionalization of bioactive phenolic compounds, offering strategic flexibility in medicinal and synthetic organic chemistry.
This case underscores phosphorous acid's potential as a cost-effective, environmentally benign, and versatile acid catalyst for C-C bond formation in phenol derivatization, contributing to the advancement of selective functionalization strategies.

Phosphorous Acid Used for the Synthesis of Quinazolinones via Metal-Free Cyclocondensation of β-Ketoesters

Li, Zhongwen, et al. The Journal of Organic Chemistry 80.19 (2015): 9392-9400.

Phosphorous acid (H₃PO₃) has emerged as an efficient and environmentally friendly catalyst for the selective synthesis of quinazolinones through cyclocondensation of β-ketoesters with o-aminobenzamides. This transformation proceeds via C-C bond cleavage under mild, metal- and oxidant-free conditions, making it particularly attractive for sustainable N-heterocycle synthesis.
In this protocol, o-aminophenyl derivatives (0.2 mmol) react with β-ketoesters or β-diketones (0.26 mmol) in the presence of 10 mol% H₃PO₃ and ethanol (0.5 mL) at 50 °C over 15 hours. After neutralization and extraction, the resulting quinazolinone products are isolated in excellent yields via column chromatography.
This phosphorous acid-catalyzed method showcases broad substrate compatibility, accommodating both 2-alkyl and 2-aryl substitutions. Notably, the strategy extends beyond quinazolinones to the efficient synthesis of other valuable N-heterocycles such as benzimidazoles and benzothiazoles, further demonstrating the versatility of H₃PO₃ as a Brønsted acid catalyst in heterocyclic chemistry.
The work highlights the unique ability of phosphorous acid to promote challenging C-C bond cleavage while avoiding transition metals and external oxidants. As such, it provides a green and practical alternative for the synthesis of pharmacologically relevant heterocyclic scaffolds, reinforcing the catalyst's utility in modern organic synthesis.

Phosphorous Acid Used for the Meyer-Schuster Isomerization of Propargyl Alcohols under Metal-Free Conditions

Gan, Xiaotang, et al. Tetrahedron Letters 60.32 (2019): 150906.

Phosphorous acid (H₃PO₃) has been effectively employed as a stoichiometric reagent in a metal-free, two-phase Meyer-Schuster isomerization, enabling the transformation of propargyl alcohols into α,β-unsaturated carbonyl compounds. This methodology provides a green and efficient alternative to traditional metal-catalyzed systems, offering high yields and excellent stereoselectivity.
In the optimized protocol, propargyl alcohols (0.2 mmol) are reacted with 50 wt% aqueous H₃PO₃ solution (0.3 mmol) in dichloromethane (0.5 mL) under nitrogen at 110 °C for 2 hours. The resulting products are isolated after a simple workup involving carbonate washing, organic extraction, and silica gel chromatography. This procedure displays a broad substrate scope, accommodating various functional groups, and proceeds under mild, transition metal-free conditions.
The key advantage of this H₃PO₃-based system lies in its operational simplicity, scalability, and avoidance of expensive or toxic metal catalysts. Moreover, the reaction offers precise control over the stereochemistry of the resulting enones, which are valuable intermediates in pharmaceuticals, agrochemicals, and fine chemicals.
This study not only underscores the catalytic potential of phosphorous acid in organic transformations but also provides a sustainable and practical alternative to the classical Meyer-Schuster reaction, thereby advancing greener synthetic methodologies in modern organic chemistry.