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Synlett 2012(8): 1170-1174  
DOI: 10.1055/s-0031-1290349
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Small Organophosphorus-Selenium Heterocycles from the Selenation of Conjugated Ketones and Enals

Guoxiong Hua, Alexandra M. Z. Slawin, J. Derek Woollins*
EastChem School of Chemistry, University of St Andrews, Fife, KY16 9ST, UK
Fax: +44(1334)463384; e-Mail: jdw3@st-and.ac.uk;
Further Information

Publication History

Received 28 November 2011
Publication Date:
10 February 2012 (online)

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Abstract

Reaction of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [Woollins’ reagent, WR] with equimolar amount of α,β-unsaturated ketones [R¹C(O)C=CR² (R¹ = aryl or alkyl; R² = ­aryl)] leads to a series of novel five-membered C3P(Se)Se hetero­cycles 1-8 in 48-95% isolated yields. Furthermore, WR reacts with one equivalent of aromatic conjugated enals [RC=CC=O, R = Ph and 2-MeOC6H4] to give five-membered C3P(Se)Se heterocycles 9 and 10 via the cleavage/cyclic extension of WR molecular ring. All new compounds have been characterised spectroscopically (³¹P NMR, 77Se NMR, ¹H NMR, ¹³C NMR, IR and mass spectroscopy) and one representative X-ray structure is reported.

Key words

selenium - phosphorus - heterocycles - Woollins’ reagent - X-Ray structure

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Crystallographic Data for Compound 1a: C21H17PSe2, M = 458.24, monoclinic, space group P21/n, a = 9.948 (3), b = 16.347 (7), c = 11.640 (4) Å, β = 102.399 (8)˚, U = 1848.7 (11) ų, Z = 4, µ = 1.646 mm-¹, 12616 reflections, 3627 unique (R int = 0.038); R 1 = 0.044, wR 2 = 0.106.

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Experimental Section: Unless otherwise stated, all reactions were carried out under an oxygen-free nitrogen atmosphere using pre-dried solvents and standard Schlenk techniques, subsequent chromatographic and workup procedures were performed in air. ¹H NMR (270 MHz), ¹³C NMR (67.9 MHz), ³¹P-{¹H} NMR (109 MHz) and 77Se-{¹H} (51.4 MHz referenced to external Me2Se) NMR spectra were recorded at 25 ˚C (unless stated otherwise) on a JEOL GSX 270 spectrometer. IR spectra were recorded as KBr pellets in the range of 4000-250 cm-¹ on a Perkin-Elmer 2000 FTIR/Raman spectrometer. Microanalysis was performed by the University of St-Andrews microanalysis service. Mass spectrometry was performed by the EPSRC National Mass Spectrometry Service Centre, Swansea and the University of St Andrews Mass Spectrometry Service. X-ray crystal data for 1, were collected using a Rigaku SCXMIni Mercury CCD system. Intensity data were collected using ω steps accumulating area detector images spanning at least a hemisphere of reciprocal space. The data were corrected
for Lorentz polarisation effects. Absorption effects were corrected on the basis of multiple equivalent reflections or by semi-empirical methods. Structures were solved by direct methods and refined by full-matrix least-squares against F² by using the program SHELXTL.²5 Hydrogen atoms were assigned riding isotropic displacement parameters and constrained to idealised geometries. The data (CCDC 855701) can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax +44(1223)336033; e-mail: deposit@ccdc.cam.ac.uk.
General Procedure for Synthesis of Compounds 1-8 from the Selenation of α , β-Unsaturated Ketones: A mixture of α,β-unsaturated ketone (1.0 mmol) and WR (0.54 g, 1.0 mmol) in anhyd toluene (20 mL) was refluxed for 7 h. Red suspension disappeared and a pale brown solution was formed along with small amount of grey elemental selenium precipitate. Upon cooling to r.t. and removing the unreacted solid by filtration the filtrate was dried in evaporator and purified by silica gel column (eluent: EtOAc-CH2Cl2, 1:1) to give compounds 1-8.
Compound 1: yellow paste (425 mg) in 92% isolated yield. IR (KBr): 1599 (m, C=C), 1490 (m), 1434 (m), 1088 (m), 749 (s), 690 (s), 595 (m), 513 (m) cm-¹. A pair of stereoisomers was found in ca. 4:6 intensity ratio. ¹H NMR (CD2Cl2): δ = 8.21 (dd, 2 × 4 H, ArH), 7.01-7.59 (m, 2 × 10 H, ArH), 6.65 (dd, J H,H = 3.6 Hz, J P,H = 32.2 Hz, 1 H, HC=C), 6.57 (dd, J H,H = 3.6 Hz, J P,H = 32.2 Hz, 1 H, HC=C), 5.52 (dd, J H,H = 3.6 Hz, J P,H = 18.2 Hz, 1 H, HC), 5.09 (dd, J H,H = 3.6 Hz, J P,H = 18.2 Hz, 1 H, HC). ¹³C NMR (CD2Cl2): δ = 142.3, 142.0, 141.8, 141.7, 136.1, 134.6, 134.1, 134.0, 133.1, 132.9, 132.8, 132.4, 132.1, 131.8, 131.7, 129.4, 129.0, 129.0, 128.8, 128.6, 128.5, 128.3, 128.2, 128.0, 127.9, 127.8, 127.3, 127.2, 125.4, 124.9, 71.6 (d, J P,C = 30.1 Hz), 65.8 (d, J P,C = 29.1 Hz). ³¹P NMR (CD2Cl2): δ = 72.4 (s, J P-Se = 346 Hz, J P=Se = 806 Hz), 71.4 (s, J P-Se = 346 Hz, J P=Se = 786 Hz). 77Se NMR (CD2Cl2): δ = 408.9 (d, J P-Se = 346 Hz), 391.5 (d, J P-Se = 346 Hz), -170.8 (d, J P=Se = 786 Hz), -187.5 (d, J P=Se = 806 Hz). MS (ESI+): m/z = 483 [M + Na]+. MS (CI+): m/z = 461 [M + H]+. HRMS (CI+): m/z [M + H]+ calcd for C21H18PSe2: 460.9471; found: 460.9473.
Compound 2: yellowish milky solid (466 mg) in 95% isolated yield. IR (KBr): 1607 (m, C=C), 1510 (s, C=C), 1435 (m), 1303 (m), 1251 (s), 1177 (m), 1090 (m), 1030 (m), 831 (m), 746 (m), 688 (m), 596 (m), 521 (m) cm-¹. A pair of stereoisomers was found in ca. 4:6 intensity ratio. ¹H NMR (CD2Cl2): δ = 8.22 (dd, J H,H = 6.9 Hz, 2 × 4 H, ArH), 6.92-7.75 (m, 2 × 10 H, ArH), 6.65 (dd, 2 × 1 H, HC=C), 5.45 (dd, J P,H = 17.6 Hz, 2 × 1H, HC), 3.80 (s, 3 H, OMe), 3.69 (s, 3 H, OMe). ¹³C NMR (CD2Cl2): δ = 141.8, 141.7, 141.4, 141.3, 136.2, 133.2, 133.0, 132.4 (d, J P,C = 3.1 Hz), 132.2 (d, J P,C = 3.1 Hz), 131.9, 131.7, 130.6, 130.5, 129.5, 129.4, 129.1, 129.0, 128.9, 128.7, 128.1, 127.9, 127.4, 127.3, 125.8, 125.3, 71.0 (d, J P,C = 31.1 Hz), 65.2 (d, J P,C = 29.1 Hz), 55.3. ³¹P NMR (CD2Cl2): δ = 73.0 (s, J P-Se = 336 Hz, J P=Se = 801 Hz), 71.6 (s, J P-Se = 345 Hz, J P=Se = 784 Hz). 77Se NMR (CD2Cl2): δ = 406.7 (d, J P-Se = 336 Hz), 390.0 (d, J P-Se = 345 Hz), -174.1 (d, J P=Se = 784 Hz), -188.2 (d, J P=Se = 801 Hz). MS (CI+): m/z = 491 [M + H]+. HRMS (CI+): m/z [M + H]+ calcd for C22H20OPSe2: 490.9577; found: 490.9582.
Compound 3: pale yellow paste (320 mg) in 81% isolated yield. IR (KBr): 1555 (w, C=C), 1489 (m), 1433 (m), 1090 (m), 764 (m), 745 (m), 689 (s), 558 (m), 526 (m), 505 (m) cm-¹. Four stereoisomers were found in ca. 4:4:2:2 intensity ratio. ¹H NMR (CD2Cl2): δ = 7.98-8.19 (m, 4 × 2 H, ArH), 6.91-7.64 (m, 4 × 8 H, ArH), 6.38-6.63 (m, 4 × 1 H, CH), 5.92-6.19 (m, 4 × 1 H, CH), 2.32-2.34 (s, 4 × 3 H, Me). ¹³C NMR (CD2Cl2): δ = 141.3, 141.1, 140.0, 139.9, 138.3, 138.2, 134.5, 134.4, 133.1, 132.9, 132.4, 132.3, 132.0, 131.7, 131.5, 129.4, 129.3, 129.1, 128.8, 128.7, 128.6, 128.4, 128.2, 128.1, 128.0, 127.9, 127.7, 125.3, 71.2, 70.8, 65.3, 64.9, 21.9, 21.2. ³¹P NMR (CD2Cl2): δ = 75.6 (s,
J P-Se = 390 Hz, J P=Se = 765 Hz), 75.3 (s, J P-Se = 336 Hz, J P=Se = 801 Hz), 74.7 (s, J P-Se = 346 Hz, J P=Se = 782 Hz), 61.7 (s,
J P-Se = 390 Hz, J P=Se = 770 Hz). 77Se NMR (CD2Cl2): δ = 449.7 (d, J P-Se = 390 Hz), 443.9 (d, J P-Se = 390 Hz), 421.4 (d, J P-Se = 336 Hz), 405.5 (d, J P-Se = 346 Hz), -111.7 (d, J P=Se = 770 Hz), -125.9 (d, J P=Se = 765 Hz), -156.7 (d, J P=Se = 782 Hz), -182.8 (d, J P=Se = 801 Hz). MS (EI+): m/z = 398 [M]+. HRMS (EI+): m/z [M]+ calcd for C16H15P76Se2: 389.9290; found: 389.99293.
Compound 4: orange solid (414 mg) in 84% isolated yield. IR (KBr): 1601 (m, C=C), 1505 (vs, C=C), 1434 (s), 1224 (s), 1158 (m), 1090 (m), 834 (s), 745 (s), 687 (m), 526 (m), 508 (s) cm-¹. A pair of stereoisomers was found in ca. 1:2 intensity ratio. ¹H NMR (CD2Cl2): δ = 8.14-8. 22 (d, J H,H = 7.2 Hz, 2 × 2 H, ArH), 6.74-7.69 (m, 2 × 11 H, ArH), 6.40-6.52 (d, 2 × 1 H, CH), 5.44-5.50 (d, 2 × 1 H, CH), 2.38 (s, 3 H, Me), 2.37 (s, 3 H, Me). ¹³C NMR (CD2Cl2): δ = 164.6, 164.3, 161.0, 160.8, 140.0, 133.1, 132.9, 132.5, 132.3, 131.8, 131.6, 131.0, 130.3, 129.9, 129.7, 129.1, 128.8, 128.6, 128.5, 128.1, 127.9, 127.6, 127.2, 127.1, 124.1, 123.8, 70.9, 70.5, 65.1, 64.6, 21.1, 21.0. ³¹P NMR (CD2Cl2): δ = 72.0 (s, J P-Se = 340 Hz, J P=Se = 803 Hz), 70.7 (s, J P-Se = 357 Hz, J P=Se = 789 Hz). 77Se NMR (CD2Cl2): δ = 400.7 (d, J P-Se = 340 Hz), 386.5 (d, J P-Se = 357 Hz), -177.8 (d, J P=Se = 789 Hz), -191.1 (d, J P=Se = 803 Hz). MS (CI+): m/z = 493
[M + H]+. MS (EI+) m/z = 492 [M]+. HRMS (EI+): m/z [M]+ calcd for C22H18FP76Se2: 483.9509; found: 483.9504.
Compound 5: yellow solid (403 mg) in 83% isolated yield. Two stereoisomers were found in ca. 1:2 intensity ratio. IR (KBr): 1598 (w, C=C), 1491 (m, C=C), 1434 (m, C=C), 1185 (w), 1165 (w), 1128 (w), 1088 (s), 939 (s), 764 (s), 745 (s), 688(vs), 630 (m), 595 (s), 506 (s, P=Se) cm-¹. ¹H NMR (CDCl3): δ = 7.47-7.63 (m, 2 × 2 H, ArH), 7.30-7.37 (m, 2 × 5 H, ArH), 7.12-7.21 (m, 2 × 4 H, ArH), 7.04-7.11 (m, 2 × 4 H, ArH), 6.93-6.96 (m, 2 × 2 H, ArH), 7.05 (d, J = 3.0 Hz, 1 H, CH), 6.95 (d, J = 3.0 Hz, 1 H, CH), 6.66 (dd, ³ J H,H = 3.0 Hz, ³ J P,H = 15.0 Hz, 1 H, CH), 6.36 (dd, ³ J H,H = 3.0 Hz, ² J P,H = 32.0 Hz, 1 H, CH). ¹³C NMR (CDCl3): δ = 141.0, 136.0, 135.8, 133.1, 133.0, 132.6, 132.4, 132.0, 129.0, 128.8, 128.3, 128.2, 127.9, 127.8, 127.0, 125.2, 70.3 (d, ¹ J P,C = 29 Hz). ³¹P NMR (CDCl3): δ = 70.3 (s, J P-Se = 338 Hz, J P=Se = 803 Hz), 69.9 (s, J P-Se = 350 Hz, J P=Se = 782 Hz). 77Se NMR (CDCl3): δ = 374.0 (d, J P-Se = 338 Hz), 354.9 (d, J P-Se = 350 Hz), -170.7 (d, J P=Se = 782 Hz), -188.0 (d,
J P=Se = 803 Hz). MS (ES+): m/z = 507 [M + Na]+. Anal. Calcd for C23H19PSe2 (484.29): C, 57.04; H, 3.95. Found: C, 57.01; H, 3.99.
Compound 6: brown solid (340 mg) in 67% yield. ³¹P NMR spectrum revealed four stereoisomers in ca. 4:2:1:2 intensity ratio. IR (KBr): 1691 (m, C=C), 1594 (m, C=C), 1518 (s, C=C), 1434 (m), 1343 (s), 1089 (m), 851 (s), 689 (s), 596 (m), 508 cm-¹. ¹H NMR (CD2Cl2): δ = 7.54-8.30 (m, 4 × 10 H, thienyl-H, ArH), 7.00-7.32 (m, 2 H, thienyl-H), 6.75-6.93 (m, 4 × 1 H, =CH), 3.26-3.44 (m, 4 × 1 H, SeCH). ¹³C NMR (CD2Cl2): δ = 150.4, 148.0, 147.7, 147.3, 143.5,142.1, 141.2, 139.2, 133.1, 133.0, 132.9, 132.7, 132.5, 132.0, 131.8, 129.1, 128.9, 128.8, 128.7, 128.6, 128.3, 128.1, 127.9, 127.8, 127.4, 127.1, 125.0, 124.6, 124.2, 123.9, 123.6, 67.6, 67.1, 61.8, 61.4, 41.1, 23.9. ³¹P NMR (CD2Cl2): δ = 73.7 (s, J P-Se = 331 Hz, J P=Se = 832 Hz), 71.8 (s, J P-Se = 340 Hz, J P=Se = 796 Hz), 61.0 (s, J P-Se = 366 Hz, J P=Se = 793 Hz), 54.1 (s, J P-Se = 380 Hz, J P=Se = 782 Hz). 77Se NMR (CD2Cl2): δ = 487.1 (d, J P-Se = 381 Hz), 473.1 (d, J P-Se = 365 Hz), 414.8 (d, J P-Se = 329 Hz), 405.6 (d, J P-Se = 341 Hz), -83.2 (d, J P=Se = 782 Hz), -161.5 (d, J P=Se = 793 Hz),
-166.7 (d, J P=Se = 796 Hz), -190.8 (d, J P=Se = 832 Hz). MS (EI+): m/z = 511 [M]+. HRMS (EI+): m/z [M]+ calcd for C19H14O2NPS74Se2: 498.8927; found: 498.8933.
Compound 7: dark red solid (250 mg)in 50% yield. ³¹P NMR spectrum revealed two stereoisomers in ca. 3:1 intensity ratio. IR (KBr): 1634 (s, C=C), 1557 (m, C=C), 1539 (m, C=C), 1470 (s), 1435 (m), 1408 (m), 1220 (m), 1071 (m), 781 (m), 748 (m), 686 (s)cm-¹. ¹H NMR (CD2Cl2): δ = 6.96-8.15 (m, 2 × 9 H, ArH), 6.41 (d, J P,H = 16.5 Hz, 1 H, CH), 6.40 (d, J P,H =16.5 Hz, 1 H, CH), 3.77-4.04 (m, 2 × 1 H, CH), 3.37 (s, 6 H, Me), 2.94 (s, 6 H, Me). ¹³C NMR (CD2Cl2): δ = 142.6, 140.5, 138.2, 134.8, 132.7, 132.5, 132.3, 132.0, 131.4, 131.2, 130.2, 130.0, 128.8, 128.6, 127.2, 126.1, 61.1, 56.6, 37.1, 34.1. ³¹P NMR (CD2Cl2): δ = 57.0 (s, J P-Se = 333 Hz, J P=Se = 787 Hz), 56.1 (s, J P-Se = 369 Hz, J P=Se = 785 Hz). 77Se NMR (CD2Cl2): δ = 455.2 (d, J P-Se = 369 Hz), 450.0 (d, J P-Se = 333 Hz), -131.2 (d, J P=Se = 785 Hz), -131.6 (d, J P=Se = 787 Hz). MS (EI+): m/z = 505 [M]+. HRMS (EI+): m/z [M]+ calcd for C17H17BrPSe2: 504.8612; found: 504.8615.
Compound 8: pale yellow solid (224 mg) in 48% yield. Multi-NMR spectrum revealed four stereoisomers in ca. 3:4:2:2 extensity ratio. IR (KBr): 1657 (s, C=C), 1432 (s), 1226 (m), 1089 (s), 819 (m), 699(vs), 595 (m), 507 (s) cm-¹. ¹H NMR (CD2Cl2): δ = 8.22-7.01 (m, 4 × 9 H, thienyl-H + ArH), 6.65-6.94 (m, 4 × 2 H, thienyl-H), 5.65-5.75 (m, 4 × 1 H, =CH), 3.29-3.29 (m, 4 × 1 H, SeCH). ¹³C NMR (CD2Cl2): δ = 144.2, 143.8, 143.6, 143.2, 138.9, 136.1, 135.2, 134.6, 133.7, 133.6, 133.0, 132.9, 132.7, 132.5, 132.4, 132.1, 131.7, 128.8, 128.3, 128.2, 128.0, 127.9, 127.3, 126.9, 125.2, 125.1, 123.7, 123.5, 44.5, 43.8, 43.3, 41.0. ³¹P NMR (CD2Cl2): δ = 71.1 (s, J P-Se = 336 Hz, J P=Se = 810 Hz), 69.1 (s, J P-Se = 341 Hz, J P=Se = 792 Hz), 61.0 (s, J P-Se = 377 Hz, J P=Se = 789 Hz), 60.5 (s, J P-Se = 393 Hz, J P=Se = 777 Hz). 77Se NMR (CD2Cl2): δ = 477.2 (d, J P-Se = 377 Hz), 412.7 (d, J P-Se = 341 Hz), 407.3 (d, J P-Se = 336 Hz), 398.5 (d, J P-Se = 393 Hz), -142.5 (d, J P=Se = 777 Hz), -166.4 (d, J P=Se = 789 Hz), -176.7 (d, J P=Se = 792 Hz), -203.3 (d, J P=Se = 810 Hz). MS (EI+): m/z = 472 [M]+. HRMS (EI+): m/z [M]+ calcd for C17H13PS2 74Se2: 459.8640; found: 459.8635.
General Procedure for Synthesis of Compounds 9 and 10 from the Selenation of Aromatic α,β-Unsaturated Enals: A red solution of aromatic enal (1.0 mmol) and WR (0.54 g, 1.0 mmol) in anhyd toluene (20 mL) was refluxed for 7 h. Red suspension disappeared and a pale brown solution along with small amount of grey elemental selenium precipitate was formed. Upon cooling to r.t. the mixture was dried in evaporator and the residue was purified by silica gel column (eluent: EtOAc-CH2Cl2, 1:5) to give compounds 9 and 10.
Compound 9: reddish yellow paste (600 mg) in 79% isolated yield. ³¹P NMR spectrum revealed a mixture of four stereoisomers in ca. 5:7:5:3 intensity ratio. IR (KBr): 1673 (s, C=C), 1491 (m), 1450 (m), 1434 (m), 1121 (m), 1088 (m), 961 (m), 764(vs), 693(vs), 591 (m), 511 (m)cm-¹. ¹H NMR (CD2Cl2): δ = 7.92-8.11 (m, 2 H, ArH), 7.07-7.58 (m, 8 H, ArH), 6.84-6.96 (m, 1 H, CH), 6.58-6.66 (m, 1 H, CH), 6.11-6.16 (m, 1 H, CH). ¹³C NMR (CD2Cl2): δ = 137.0, 136.7, 134.0, 133.5, 133.4, 132.4, 132.2, 132.0, 131.6, 130.7, 129.6, 129.5, 129.0, 128.9, 128.7, 128.6, 128.4, 128.2, 128.1, 127.9, 127.5, 126.6, 32.0. ³¹P NMR (CD2Cl2): δ = 72.6 (s, J P-Se = 326 Hz, J P=Se = 802 Hz), 72.1 (s, J P-Se = 336 Hz, J P=Se = 784 Hz), 55.6 (s, J P-Se = 383 Hz, J P=Se = 770 Hz), 55.5 (s, J P-Se = 383 Hz, J P=Se = 767 Hz). MS (CI+): m/z = 385 [M + H]+. HRMS (CI+): m/z [M + H]+ calcd for C15H14PSe2: 384.9160; found: 384.9159.
Compound 10: greyish yellow solid (230 mg) in 56% isolated yield. ³¹P NMR spectrum revealed a pair of stereoisomers in ca. 1:2 intensity ratio. IR (KBr): 1597 (m, C=C), 1490 (s), 1460 (s), 1434 (m), 1244(vs), 1026 (m), 750 (s) cm-¹. ¹H NMR (CD2Cl2): δ = 7.02-8.20 (m, 2 × 6 H, thienyl-H + ArH), 6.83-6.99 (m, 2 × 3 H, thienyl-H), 6.37-6.51 (m, 2 × 1 H, =CH), 5.38-5.44 (m, 2 × 1 H, PCH), 3.87 (s, 3 H, OMe), 3.80 (s, 3 H, OMe), 3.29-3.45 (m, 2 × 1 H, SeCH). ¹³C NMR (CD2Cl2): δ = 157.4, 156.5, 148.0, 146.0, 133.7, 133.6, 132.0, 131.9, 131.7, 131.5, 129.7, 129.4, 129.3, 129.2, 129.1, 128.5, 128.3, 128.0, 127.9, 127.4, 127.3, 127.2, 127.0, 58.1, 57.6, 55.6, 55.5. ³¹P NMR (CD2Cl2): δ = 71.9 (s, J P-Se = 322 Hz, J P=Se = 798 Hz), 75.1 (s, J P-Se = 315 Hz, J P=Se = 782 Hz). 77Se NMR (CD2Cl2): δ = 410.8 (d, J P-Se = 322 Hz), 381.6 (d, J P-Se = 315 Hz), -91.4 (d, J P=Se = 782 Hz), -183.8 (d, J P=Se = 798 Hz). MS (CI+): m/z = 415 [M + H]+. HRMS (CI+): m/z [M + H]+ calcd for C16H16OPSe2: 414.9265; found: 414.9264.