Halogenation of Dibenzoselenophene and Dibenzo[1,2]diselenine 

Abstract

The syntheses of the selenium containing heterocycles dibenzoselenophene (1 ≡ biphenSe) and dibenzo[1,2]diselenine (2 ≡ biphenSe2) were optimized. The halogenation reactions of 1 and 2 with XeF2, SO2Cl2, Br2 and I2 were performed and the corresponding products characterized. In the case of 1, the selenium(IV) dihalogenides, biphenSeF2 (3), biphenSeCl2 (4), biphenSeBr2 (5), and the adduct biphenSe·I2 (6), were isolated and identified. The extremely sensitive selenium(IV) difluoride 3 slowly formed significant amounts of an adduct with HF of the corresponding selenium(IV) oxide biphenSeO·HF (3a) upon storage in glass vessels at low temperatures. In the case of 2, the selenium(IV) trihalogenides, biphen(SeHal3)2 (Hal = F, Cl, Br), were found to be extremely labile (Hal = F) or not detectable (Hal = Cl, Br). Instead, as decomposition products, the selenium chloride species Se2Cl2, SeCl4 and 1 were detected. In the case of Hal = I, the stable adduct biphenSe2·I2 (7) was isolated. In addition to characterization by multinuclear NMR spectroscopy, several molecular structures of biphen‐selenium substituted halogenides were determined.

Conversion of 2‐Iodobiaryls into 2,2′‐Diiodobiaryls via Oxidation‐Iodination Sequences: A Versatile Route to Ladder‐Type Heterofluorenes

“…These results suggest great promise for ac atalyst system based on copper and elemental sulfur/selenium to prepare dibenzothiophenes and dibenzoselenophenes directly from 2,2'-diiodobiaryls. [27] Atwofold iodine-lithium exchange/electrophilic trapping sequence proved effective for the preparation of germanium-and phosphoryl-bridged p-teraryls 12 and 13, [15a, 28] respectively.T he latter product was obtained as as eparable mixture of syn-a nd anti-isomers.B esides the heteroatom-bridged p-teraryls,t he Pd-catalyzed reaction of 6b with 5-decyne,u sing Wus conditions, [29] resulted in atwofold annulation to afford benzo[k]tetraphene derivative 14.Single-crystal X-ray diffraction analysis was performed for all of these ladder-type products except anti-13,w hich invariably demonstrated high levels of coplanarity of their . .…”

Conversion of 2‐Iodobiaryls into 2,2′‐Diiodobiaryls via Oxidation‐Iodination Sequences: A Versatile Route to Ladder‐Type Heterofluorenes

“…As imilar Cu-catalyzed method using selenium and (N-methyl-2-pyrrolidone) (NMP) instead of sulfur and DMF [18a] allowed conversion of 6b and 9 into benzo [1,2- (15). [27] Atwofold iodine-lithium exchange/electrophilic trapping sequence proved effective for the preparation of germanium-and phosphoryl-bridged p-teraryls 12 and 13, [15a, 28] respectively.T he latter product was obtained as as eparable mixture of syn-a nd anti-isomers.B esides the heteroatom-bridged p-teraryls,t he Pd-catalyzed reaction of 6b with 5-decyne,u sing Wus conditions, [29] resulted in atwofold annulation to afford benzo[k]tetraphene derivative 14.Single-crystal X-ray diffraction analysis was performed for all of these ladder-type products except anti-13,w hich invariably demonstrated high levels of coplanarity of their Scheme 3. a) Conversiono f2',5'-diiodo-p-terphenyl derivatives 4a-4d to 2,2',2'',5'-tetraiodo-p-terphenyl derivatives 6a-6d,a nd b) conversion of 2,5-bis(2-iodophenyl)thiophene 7 to 3,4-diiodo-2,5-bis(2-iodophenyl)thiophene 9.Reaction conditions: i) mCPBA (3 equiv), TfOH (6 equiv), CH 2 Cl 2 ,RT, 2h;i i) CuI (20 mol %), L1 (40 mol %), [(nBu) 4 N]I (4 equiv), MeCN, 60 8 8C, 24 h. Inset:O RTEP drawing of 5b (thermal ellipsoids set at 50 %p robability), whereby hydrogen atoms, counteranions, and solvent molecules were omitted for clarity. [27] Atwofold iodine-lithium exchange/electrophilic trapping sequence proved effective for the preparation of germanium-and phosphoryl-bridged p-teraryls 12 and 13, [15a, 28] respectively.T he latter product was obtained as as eparable mixture of syn-a nd anti-isomers.B esides the heteroatom-bridged p-teraryls,t he Pd-catalyzed reaction of 6b with 5-decyne,u sing Wus conditions, [29] resulted in atwofold annulation to afford benzo[k]tetraphene derivative 14.Single-crystal X-ray diffraction analysis was performed for all of these ladder-type products except anti-13,w hich invariably demonstrated high levels of coplanarity of their Scheme 3. a) Conversiono f2',5'-diiodo-p-terphenyl derivatives 4a-4d to 2,2',2'',5'-tetraiodo-p-terphenyl derivatives 6a-6d,a nd b) conversion of 2,5-bis(2-iodophenyl)thiophene 7 to 3,4-diiodo-2,5-bis(2-iodophenyl)thiophene 9.Reaction conditions: i) mCPBA (3 equiv), TfOH (6 equiv), CH 2 Cl 2 ,RT, 2h;i i) CuI (20 mol %), L1 (40 mol %), [(nBu) 4 N]I (4 equiv), MeCN, 60 8 8C, 24 h. Inset:O RTEP drawing of 5b (thermal ellipsoids set at 50 %p robability), whereby hydrogen atoms, counteranions, and solvent molecules were omitted for clarity.…”

Noble gases

“…+10 cm À1 ) of the H-Y and H-Xe stretching frequencies were observed for the complexes with respect to the monomers. 16 Treatment of XeF 2 with cyclotron-produced [ 18 F]fluoride ion produced [ 18 F]XeF 2 , which is a potentially useful agent for labeling novel radiotracers for imaging applications that employ positron emission tomography (PET). For the lighter noble gases (He and Ne), electronically excited reactant ions were observed, whereas single-electron transfers were involved for reaction pathways of the Kr and Xe analogues.…”