Efficient synthesis of unsymmetrical diaryl thioethers via TBAF-mediated denitrative substitution of nitroarenes with PhSTMS under mild and neutral conditions

DABCO Mediated Sulfur Activation‐Intramolecular De‐Nitration Strategy for the Synthesis of Novel Dihydrothiochromeno[4,3‐c]pyrazoles

“…Thereafter, we screened different catalysts such as KI, I 2, PTSA, In(OTf) 3 to test the efficiency of this transformation, but the reaction could not deliver the desired product 4 aA and the model substrates remained intact even after 24 hours (Table 1, entries [8][9][10][11]. The efficiency of transition-metal catalysts such as CuSO 4 .5H 2 O, Cu(OAC) 2, and CuBr 2 was also examined, however, satisfactory results were not delivered (Table 1, entries [11][12][13][14]. Similar results were obtained when a series of protic and aprotic solvents like DMF, ACN, THF, 1,4-dioxane, MeOH, and toluene were screened (Table 1, entries [15][16][17][18][19].…”

“…The product was air dried under vacuum to yield an off-white product, ( 3 The organic layers were combined, dried over anhydrous Na 2 SO 4, and concentrated under reduced pressure to yield the crude compound which was passed through a short silica gel column (60-120 mesh) using EtOAc/hexane (10/90; v/v) as an eluent to afford 4 aA as a yellow solid (0.11 g; 74%). 3, 124.8, 126.9, 127.9, 128.1, 128.4, 130.2, 130.4, 131.0, 132.8, 133.0, 137.3, 149.4, 150.1, 183.6 , 119.6, 122.7, 124.3, 126.5, 127.7, 129.9, 130.0, 130.6, 132.4, 132.9, 135.2, 139.5, 149.9, 183. 72 (m, 3H, ArH), 8.14 (dd, J = 7.9, 1.9 Hz, 1H, ArH), 8.48 (s, 1H, ArH), 9.86 (s, 1H, CHO) ppm; 13 C NMR (150 MHz, CDCl 3 ) δ = 121.0, 123. 2, 124.8, 126.8, 130.0, 130.3, 132.1, 132.8, 133.1, 134.0, 137.5, 150.5, 183.5 123.9, 126.3, 129.6, 132.2, 132.5, 134.7, 148.6, 148.9, 161 2, 119.8, 122.8, 124.8, 127.1, 130.1, 130.4, 132.1, 132.9, 133.0, 136.7, 138.3, 150.1, 183.6 6, 124.9, 126.7, 128.5, 128.6, 129.0, 130.3, 130.8, 132.8, 133.1, 135.6, 135.8, 137.1, 149.4, 150.3, 183.5 8, 119.8, 121.3, 124.1, 126.3, 127.8, 128.2, 129.1, 129.7, 131.9, 132.1, 132.4, 132.7, 132.8, 137.3, 137.4, 148.9, 149.2, 188.8 , 119.0, 119.5, 121.6, 124.9, 127.2, 127.6, 128.5, 128.7, 130.0, 130.2, 132.8, 133.0, 134.1, 137.1, 137.7, 138.2, 149.6, 149.7, 190.0…”

“…Yield:74% (0.190 g from 0.200 g) as a light yellow solid; m.p. 158-160 °C; R f = 0.74 (hexane/EtOAc, 70 : 30, v/v); IR (neat): ν max (cm À 1 ) = 1215 (CH=CH), 1355, 1528 (NO 2 ), and 1662 (C=O); 1 H NMR (600 MHz, CDCl 3 ) δ = 7.14 (d, J = 15.7 Hz, 1H, =CH), 7.39 (dd, J = 8.6, 2.3 Hz, 1H, ArH), 7.45 (t, J = 7.7 Hz, 2H, ArH), 7.54-7.56 (m, 1H, ArH), 7.58-7.67 (m, 5H, =CH and ArH), 7.73-7.76 (m, 1H, ArH), 7.85 (dd, J = 8.3, 1.2 Hz, 2H, ArH), 8.10 (dd, J = 8.2, 1.1 Hz, 1H, ArH), 8.32 (s, 1H, ArH) ppm; 13 C NMR (150 MHz, CDCl 3 ) δ = 118. 8, 122.2, 125.0, 127.2, 128.4, 128.5, 128.7, 128.8, 130.2, 130.7, 131.9, 132.7, 132.9, 133.1, 133.7, 135.2, 136.0, 138.1, 149.7, 149.8, 190.0 21.1, 118.8, 119.5, 120.8, 123.0, 124.9, 127.0, 127.4, 130.2, 130.3, 131.5, 132.8, 133.1, 134.9, 135.6, 137.0, 137.7, 140.1, 149.7, 188.5 , 118.8, 119.5, 120.9, 124.9, 127.3, 127.5, 127.9, 130.0, 130.3, 132.0, 132.8, 133.1, 134.6, 137.0, 137.7, 149.7, 188.9…”

“…Yield: 80% (0.220 g from 0.200 g) as a yellow solid; m.p. 168-170 °C; R f = 0.69 (hexane/EtOAc, 70 : 30, v/v); IR (neat): ν max (cm À 1 ) = 1215 (CH=CH), 1360, 1533 (NO 2 ), and 1655 (C=O); 1 H NMR (600 MHz, CDCl 3 ) δ = 2.40 (s, 3H, CH 3 ), 2.41 (s, 3H, CH 3 ), 7.16 (d,J = 15.7 Hz,1H,=CH),7.25 (s,1H,ArH),7.28 (d,J = 8.3 Hz,3H,ArH),5H,=CH and ArH),1H,ArH),7.78 (d,J = 8.2 Hz,2H,ArH),8.08 (dd,J = 8.1,1.0 Hz,1H,ArH),8.31 (s,1H,ArH) ppm; 13 C NMR (150 MHz, CDCl 3 ) δ = 21.1, 21.8, 119.1, 119.5, 121.6, 124.9, 127.1, 127.6, 128.6, 129.4, 130.0, 130.2, 132.9, 133.0, 133.6, 135.7, 137.1, 137.6, 143.7, 149.5, 149.7, 189.5…”

“…Accordingly, in these transformations, [12] the involvement of either transition-metal catalysts such as Cu, Rh, and Pd or highly activating groups is required. [13] The majority of methods for the synthesis of sulfaheterocycles frequently use the pre-functionalised thiols. [14] Moreover, alternative approaches require the addition of external sulfur atoms from effective sulfur sources, such as potassium ethyl xanthate, potassium thiosulfate, potassium sulfide, dimethyl sulfoxide, and potassium thiocyanate.…”