Synthesis of Pinpoint‐Fluorinated Polycyclic Aromatic Hydrocarbons: Benzene Ring Extension Cycle Involving Microwave‐Assisted S_NAr Reaction

Abstract

Fluoroarenes bearing no electron-withdrawing groups (non-activated fluoroarenes) readily underwent nucleophilic aromatic substitution with α-cyanocarbanions under microwave irradiation. The sequence (i) formylalkylation involving the cyanoalkylation of fluoroarenes, (ii) difluorovinylidenation, and (iii) Friedel-Crafts-type cyclization, afforded extended fluoroarenes by one benzene ring per cycle. Furthermore, the performance of multiple cycles successfully provided higher-order pinpoint-fluorinated polycyclic aromatic hydrocarbons (F-PAHs).

Gold-catalyzed electrophilic activation of 1,1-difluoroallenes: α- and γ-selective addition of heteroatom nucleophiles

“…N- (1,1-difluoro-5-phenylpent-1-en-3-yl)benzamide (6) 1 H NMR (500 MHz, CDCl 3 ): δ 1.91-2.00 (m, 1H), 2.05-2.14 (m, 1H), 2.65-2.76 (m, 2H), 4.37 (ddd, J = 8.0, 2.2 Hz, J HF = 24.6 Hz, 1H), 4.81 (tdd, J = 8.0, 8.0, 8.0 Hz, 1H), 6.26 (d, J = 8.0 Hz, 1H), 7. 3H),7.28 (dd,J = 7.8,7.8 Hz,2H),7.39 (dd,J = 7.7,7.7 Hz,2H),7.48 (dd,J = 7.5,7.5 Hz, 1H), 7.67 (d,J = 7.3 Hz,2H); 13 C NMR (126 MHz, CDCl 3 ): δ 32.2, 36.9, 44.7 (d, J CF = 7 Hz), 80.2 (dd, 22,19 Hz),126.1,126.8,128.3,128.5,128.6,131.6,134.2,140.9,156.9 (dd 301.1278;found: 301.1270. 4.3.10.…”

“…1 H NMR (500 MHz, CDCl 3 ): δ 1.87 (dddd, J = 18.0, 8.4, 5.9, 5.9 Hz, 1H), 2.02-2.10 (m, 1H), 2.70 (ddd, J = 14.0, 9.2, 6.8 Hz, 1H), 2.78 (ddd, J = 14.0, 9.4, 5.9 Hz, 1H), 3.76-3.83 (m, 1H), 4.21 (ddd, J HF = 24.1 Hz, J = 10.8, 2.0 Hz, 1H), 7.16 (d,J = 7.5 Hz,2H),7.20 (t,J = 6.8 Hz,1H),5H),2H); 13 C NMR (126 MHz, CDCl 3 ): δ 33. 3,36.6,42.3 (d,J CF = 6 Hz),81.3 (dd,J CF = 23,19 Hz),126.1,127.7,128.4,128.5,128.9,133.3,133.4,140.8,157.0 (dd, J CF = 290, 290 Hz); 19…”

C-F bond activation under transition-metal-free conditions

“…In analogy to previous protocols which utilized i Bu 2 AlH or LiGaH 4 (vide supra), Weaver and co-workers [62] reported the HDF of perfluoroarenes with NaBH 4 (Scheme 20). The advantage of this reaction is that it is compatible with both EDG and EWG substituted substrates (103)(104)(105)(106)(107)(108)(109)(110)(111)(112)(113)(114). Specifically, the use of NaBH 4 rather than more potent reductant LiAlH 4 allowed for the incorporation of ester ( 103) and amide (104).…”

“…Ichikawa's group [102][103][104][105][106] developed a series of Friedel-Crafts-type cyclization of 1,1-difluoroallenes to synthesize helicenes and polycyclic aromatic hydrocarbons (PAHs) (Scheme 37). Utilizing highly acidic reagents such as magic acid (FSO 3 H•SbF 5 ) and TfOH, or Lewis acid TiF 4 , the 1,1difluoroalkenes were successfully converted into desired products via the generation of the CF 2 cations.…”

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

“…We have already achieved the metal-catalyzed and acid-mediated cationic cyclization of 1,1-difluoro-1-alkenes. In the former case, we reported the palladium [ 6 – 10 ], indium [ 10 – 13 ], and silver-catalyzed construction of ring-fluorinated carbocycles and heterocycles [ 14 ]. In the latter case, the domino-Friedel–Crafts-type cyclization proceeded via the cleavage of two carbon–fluorine bonds to afford polycyclic aromatic hydrocarbons [ 15 – 21 ].…”