P-O Bond Formation
TfOH catalyzes wet and dry processes for converting phosphonate esters to phosphonic acids in good yields. Whereas in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be hydrolyzed to the corresponding phosphonic acids at 140°C, the conversion of dibenzyl phosphonates to the corresponding phosphonic acids takes place smoothly at 80°C in toluene.
C. Li, Y. Saga, S.-y. Onozawa, S. Kobayashi, K. Sato, N. Fukaya, L.-B. Han, J. Org. Chem., 2020, 85, 14411–14419.
Monosubstituted phosphinic acids can be esterified with orthosilicates in excellent yields. Whereas phosphinylidene-containing acids react selectively, disubstituted phosphinic acids and phosphonic acids remain unchanged. This method provides a convenient and general alternative to more commonly employed reactions with diazomethane or carbodiimide.
Y. R. Dumond, R. L. Baker, J.-L. Montchamp, Org. Lett., 2000, 2, 3341-3344.
Phosphorylation of amines, alcohols, and sulfoximines provides various phosphoramidates, phosphorus triesters and sulfoximine-derived phosphoramidates using molecular iodine as a catalyst and H2O2 as the sole oxidant under mild reaction conditions.
J. Dhineshkumar, K. R. Prabhu, Org. Lett., 2013, 15, 6062-6065.
A simple visible-light photocatalytic reaction of N-alkoxypyridinium salts with phosphites provides a broad range of phosphate esters under mild conditions. The protocol was successfully applied to the synthesis of biologically relevant structures.
A. Inial, F. Morlet-Savary, J. Lalevée, A.-C. Gaumont, S. Lakhdar, Org. Lett., 2020, 22, 4404-4407.
A metal-, toxic chloride reagent-free activating strategy of various phosphates with Tf2O and pyridine enables a facile synthesis of functional phosphates such as alkyl phosphates, aza phosphates, thiophosphate, and mixed diaryl phosphates via a transient phosphorylpyridin-1-ium species.
H. Huang, J. Ash, J. Y. Kang, Org. Lett., 2018, 20, 4983-4941.
A selective three-step substitution transesterification starting with tris(2,2,2-trifluoroethyl) phosphate enables the facile synthesis of mixed unsymmetric phosphate triesters from three different alcohols. The substitution of the trifluoroethoxy group at the phosphorus proceeds selectively in the presence of DBU or lithium alkoxides.
K. Tsubaki, H. Shimooka, M. Kitamura, T. Okauchi, Org. Lett., 2019, 21, 9779-9783.
Reaction of phosphorus oxychloride with a primary alcohol and triethylamine in toluene, followed by filtration and treatment with steam, gives dialkyl phosphates in good yield and essentially free from trialkyl phosphate impurities.
R. A. Aitken, C. J. Colett, S. T. E. Mesher, Synthesis, 2012, 44, 2515-2518.
An efficient electrophilic fluorination of secondary phosphine oxides with Selectfluor provides direct access to phosphoric fluorides in good yield under mild conditions. In addition, one-pot P-O bond construction is achieved in the presence of water or alcohols to provide phosphinic acids or phosphinates.
Q. Chen, J. Zeng, X. Yan, Y. Huang, C. Wen, X. Liu, K. Zhang, J. Org. Chem., 2016, 81, 10043-10048.
An electrochemical cross-dehydrogenative-coupling reaction between alcohols and secondary phosphine oxides provides organophosphinates in an eco-friendly and efficient manner at room temperature without the addition of any oxidant, metal catalyst, or additive.
L. Deng, Y. Wang, H. Mei, Y. Pan, J. Han, J. Org. Chem., 2019, 84, 949-956.
Addition of P-H species to carbonyl groups, namely the Pudovik reaction, normally delivers hydroxyl phosphorus compounds. A few systems starting from phosphites provide the phosphates. Cs2CO3 mediates a highly selective synthesis of phosphinate derivatives starting from phosphonate precursors.
Y. Qian, Q. Dai, Z. Li, Y. Liu, J. Zhang, Org. Lett., 2020, 22, 4742–4748.
Bis(dimethylamino)phosphorodiamidate enables an efficient one-pot cyclophosphorylation of vicinal cis-diol moieties of biologically interesting polyols without the need for protecting group chemistry. The reaction is amenable to large-scale reactions.
M. Yadav, R. Krishnamurthy, Org. Lett., 2019, 21, 7400-7404.
Copper catalysis allows the direct oxygen-arylation of dialkyl phosphonates with diaryliodonium salts. This reaction proceeds with a wide range of phosphonates and phosphoramidates under mild conditions and gives mixed alkyl aryl phosphonates in very good yields and very good selectivity.
M. Fañanás-Mastral, B. L. Feringa, J. Am. Chem. Soc., 2014, 136, 9894-9897.