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SPOTLIGHT 2245

SYNLETT Phosphorus Pentasulfide (P4S10) Spotlight 99 Compiled by Vivek Polshettiwar

This feature focuses on a re- Vivek Polshettiwar was born in Mangli (Village) Maharashtra (India) in 1979. He completed his B.Sc. (1999) and M.Sc. (2001) agent chosen by a postgradu- degrees in organic chemistry from Amravati University, Amravati, ate, highlighting the uses and India. He is currently working as a DRDO-SRF for his Ph.D. under preparation of the reagent in the supervision of Prof. M. P. Kaushik at Defence R & D current research Establishment in Gwalior, India. Process Technology Development Division, Defence R & D Establishment, Jhansi Road, Gwalior, 474002 (MP) India. E-mail: [email protected] Dedicated to my guide, Prof. M. P. Kaushik, on his 50th birthday.

Introduction

Organosulfur compounds are valued not only for their S rich and varied chemistry, but also for many important S P S biological properties. Phosphorous pentasulfide (P4S10) is very useful and versatile reagent for the synthesis of S PPS S various organosulfur compounds. P4S10 is widely avail- S able as a light yellow crystalline solid. It is highly flam- S P S mable and decomposes in the presence of moisture. S

P4S10 has been extensively used as a thionating agent for the conversion of carbonyls into thiocarbonyls in the preparation of organosulfur compounds. It also activates the free hydroxyl group of an acid or an alcohol to create a good leaving group. It can also be used as a deoxygenating and dehydrating agent.

Abstracts

(A) As a thionating agent: Various carbonyl groups can be con- S verted into the corresponding thiocarbonyl groups by treatment 1 with P4S10. Recently, the combination of P4S10 and HMDO has R NH2 2 proved to be a very useful thionating reagent over P4S10 alone. O O

R NH2 SS S R OR' 1 P4S10/HMDO R S O O R OR' R2 O R1 OEt R2 R R'

S This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. R R'

(B) In the synthesis of Lawesson’s reagent: The most popular OMe S S thionating reagent can be synthesized by reaction of P4S10 with 3 + P2S5 MeO P P OMe anisole. 2 h, 82% S S Lawesson's Reagent

SYNLETT 2004, No. 12, pp 2245–2246 01.10.2004 Advanced online publication: 21.09.2004 DOI: 10.1055/s-2004-832833; Art ID: V10203ST © Georg Thieme Verlag Stuttgart · New York SPOTLIGHT 2246

(C) As an activating agent: P4S10 activates the free hydroxyl group O O H P S , Py of carboxylic acids or alcohols to create a good leaving group. MeO N 4 10 MeO When this activation is done in the presence of another nucleo- OH N + phile, a substitution reaction occurs.4 It is also used for the syn- HO 2.5 h, 70% HO O O thesis of dithiocarboxylic esters.5 OMe OMe

O S P4S10 + R'' XH R' OH X = O , S Toluene R' SR''

(D) As a deoxygenating agent: P4S10 is one of the mildest selective OPh OPh reagents for the conversion of sulfoxides to sulfides.6 The reduc- O O O tion takes place selectively without affecting functional groups P4S10, Py such as esters, amides or ketones. Interestingly, sulfones are also HN S 25 °C, 16 h HN S 7 unreactive under these conditions. N 90% N O O CO2Me CO2Me

(E) As a dehydrating agent: Use of P4S10 as a dehydrating agent Ph Ph P4S10, CS2 has been reported. The aromatization of a furan Diels–Alder 25 °C, 70 h adduct using P4S10 in CS2 has been found to be superior than with O other reagents like HCl/HOAc or polyphosphoric acid.8 61% Ph Ph

(F) As an adduct: The reaction of steroidal molecule 16-dehydro- Me pregnenolone acetate (16-DPA) with P4S10 in refluxing benzene AcO O Me P SS afforded a novel adduct 16-DPA–P2S5. This adduct undergoes O S S O [4+2] cycloaddition with alkyne dienophiles to afford biologically H P Me 9 P4S10, Benzene S active steroidal (17,16-c)pyrans. H Reflux, 4 h AcO

OAc

(G) In the synthesis of thiolactams: Phosphorus pentasulfide reacts S O under mild conditions with organolithiums to give solutions in tet- rahydrofuran. This in situ reagent converts lactams to thiolactams 10 and shows significant selectivity in the type of reactive lactams. THF, 10 °C to reflux HN HN + P4S10 + RLi 25–87%

(H) In the synthesis of episulfides: Sterically hindered methyl- O R enecyclopropanones can be thionated with P4S10 in pyridine to S R R R R afford novel 1,2,3-butatriene episulfides and a thiiranoradialene R P4S10 S R 11 derivative. Py or R R R R R R, R = t-Bu, R, R =

References This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. (1) (a) Hurd, R. N. Chem. Rev. 1961, 61, 45. (b) Polshettiwar, (6) Madesclaire, M. Tetrahedron 1988, 44, 6537. V.; Kaushik, M. P. Tetrahedron Lett. 2004, 45, 6255. (7) Micetich, R. C. Tetrahedron Lett. 1976, 17, 971. (2) Curphey, T. J. J. Org. Chem. 2002, 67, 6461. (8) Cava, M. P.; VanMater, J. P. J. Org. Chem. 1969, 34, 538. (3) Thomsen, I.; Clausen, K.; Scheibye, S.; Lawesson, S. O. (9) Chetia, A.; Saikia, A.; Saikia, C. J.; Boruah, R. C. Org. Synth. 1984, 64, 158. Tetrahedron Lett. 2003, 44, 2741. (4) Blade-Font, A.; Aquila, S.; De Mas, T.; Torres, J. M. (10) Goel, O. P.; Krolls, U. Synthesis 1987, 162. J. Chem. Res. (S) 1981, 58. (11) Ando, W.; Hayakawa, H.; Tokitoh, N. Tetrahedron Lett. (5) Sudalai, A.; Kanagasabapathy, S.; Benicewicz, B. C. Org. 1987, 28, 1803. Lett. 2000, 2, 3213.