P4S10 PHOSPHORUS PENTASULFIDE

P4S10 PHOSPHORUS PENTASULFIDE 18.3195 -5.1772E+03 -3.3346E+00 1.0110E-03... 

P4S10 PHOSPHORUS PENTASULFIDE -25.525 2.3950E+00 -6.9192E-03 9.9713E-06 -5.3678E-09 30 560 solid... 

Although phosphorus trisulfide (P4S6—but see below) and phosphorus pentasulfide (P4S10) have been widely used in the preparation of heterocyclic compounds there is no recent review. Weintraub has given an account of solvent- and temperature-dependent reactions of the pentasulfide, the compound employed in almost all recently reported work.118... 

Thioamides and their use in the preparation of the heterocyclic compounds are widely reported in the literature. Also they attract considerable interests in peptide chemistry. Molecular and crystal structures of some thioamide derivatives have been confirmed by X-ray diffraction data.8 10 Lawesson s reagent or phosphorus pentasulfide (P4S10) is actively used for the synthesis of thio-carbonyl compounds. Their preparation methods, reactions, applications in the synthesis of heterocycles and biological effects are mainly described in this section. 

Direct thionation of amino acid derivatives has been achieved using P4S10. Direct thionation of anilide has been achieved with a mixture of P4S10 and anhydrous Na2C03 in THF.19 Selective thionation of amide has been achieved using P4S10 in THF under ultrasound irradiation. By-product is absent from the phosphorus pentasulfide thionation. Thionation of the amide with Lawesson s reagent is less selective (Scheme 4).20... 

Phosphorus pentasulfide (P4S10) has also been used in construction of a new thiophene ring by the introduction of sulfur. Dipolar addition of dibenzoylacetylene to the mesoionic anhydro-4-hydroxy-2,3,5-triphenylthiazolium hydroxide (260) gave 3,4-dibenzoyl-2,5-diphenylthiophene (151), which upon reaction with P4Si0 in dry pyridine gave tetraphenylthieno[3,4-c]thiophene (6 Scheme 89) (77HC(30)317). 

In a related approach, a, /i-unsaturated thioketones, formed in situ by thionation with P4S10 of the corresponding ketones, undergo intramolecular hetero-Diels-Alder reactions263. Diethyl thioxomalonate was formed from diethyl oxomalonate and phosphorus pentasulfide (equation 29) and was trapped as a Diels-Alder adduct264. 

Acylamino ketones also provide a convenient synthesis of thiazoles on treatment with phosphorus pentasulfide (Gabriels method). Substituents are usually restricted to alkyl, aryl, and alkoxy derivatives. Thus, the -acylamino ketone 234 with P4S10 gave the thiazole 240. Lawessons reagent (LR) can be effectively used as the source of sulfur in these cyclizations (e.g., Scheme 116) <1996JME957, 2006TL2361, CHEC-III(4.06.9.1.3)682>. 

The substitution of the hydroxy group by a thiol group (or transformation of the oxo form into the thioxo form) is achieved by treatment with phosphorus pentasulfide (P4S10) in pyridine at reflux temperature. In the case of pyrimido[4,5-c/]pyridazine-2,4-diol (3) it is possible to exchange only the 4-hydroxy group or both hydroxy groups57. 

LR is commercially available but can also be readily synthesized in the laboratory by heating anisole with phosphorus pentasulfide (P4S10), until the mixture is clear and no more HjS evolves, followed by recrystallization from toluene or xylene. Suggest a mechanism for the reaction. 

Other interesting methods can generate furans. One method treats an allylic diol such as 125 with pyridinium chlorochromate (PCC see Chapter 17, Section 17.2.3), in an oxidative-cyclization process, to give 3-ethylfuran, 126. Thiophene derivatives can also be prepared from 1,4-dicarbonyl compounds. A Paal-Knorr thiophene synthesis reacts 2,4-hexanedione (115) with phosphorus pentasulfide (P4S10) to give 2,5-dimethylthiophene, 127. 

Phosphorus pentasulfide-pyridine complex (P4S10, 68) has been used as a thionating agent for transformation of one carbonyl group in (67) to the corresponding thionated derivative (69) (Scheme 14). ... 

---