Isobenzofulvenes

Abstract

azatriafulvalenium salts ( l o ) , m.p. 222 OC (dec.); h : : ; C N = 390 nm, log E = 1835 cm-1, ( I I a ) , m.p. 235 OC (dec.); A : : . " " = 372 nm, log E = 4.18; vc=c = 1840 cm-1, and ( I l b ) , m.p. 205 O C (dec.); h:F;CN = 362 nm (shoulder), log E = 4.09, vc=c = 1825 cm-1, are obtained in yields of 79, 50, and 59 % respectively. They are deprotonated t o give the 4.70; vc. Compound la1 (15) 115') (16d (16at) (166) (17) (18) Clop clop (10) (lla), R = H (Ilb), R = CsH5 azacalicenes (10') [ A : ! ; ' " = 384 nm, log E = 4.63; vc=c = 1835 cm-11. ( I l a ' ) [unstable red oil], and (11%) [dark red solution]; (10) and ( I l a ) by Hunig base in methylene chloride, ( I l b ) by potassium tert-butoxide. The action of tropylium perchlorate on 2,4-diphenylpyrrole under various conditions always gives a 1 : 2 adduct in a yield of about 15 %. This adduct can be isolated as the perchlorate ( I 2 ) , m.p. 282'C (dec.); = 554 nm, log E = 4.83. The free base is obtained from (12) with Hiinig base (m.p. 279OC; = 520 nm, log E = 4.67). Compound (12) gives a red-violet anion with potassium rert-butoxide. Yield ( %) 62 80 55 30 30 H Cl0,Q 265 [cl 187 226 [cl 208 174 235Benzoheterofulvalenes are obtained by reaction of pyrroles and indoles with the benzo-derivatives of the cations (11-13).The N a salt of 4,5-diphenylimidazole, which is prepared by heating diphenylimidazole with N a H in benzene in the presence of a little diglyme, reacts surprisingly smoothly with ( I ) and (2) in boiling benzene t o form the diazadithiafulvalenes (131 (red needles, m.p. 21OoC, yield 35 %) and (14) (m.p. 205 O C ; = 565 nm, log E = 4.60; yield 49 %). (14) forms a perchlorate [m.p. 280 "C (dec.); h:F;' " = 520 nm, log E = 4.571; reaction with an excess of perchloric 380 300-500 Id] 466 347 550 3 74 300-450 [d] 410 H acid gives the dication (14)2+ (h:~;cN-HC'04 = 460 nm, log E = 4.40). Compound (13) behaves in a similar manner.Di-and triphenylpyrroles react with benzophenone dichloride in acetonitrile at room temperature t o give the azafulvenes (15) and (16), which are isolated as the perchlorates and are deprotonated with Hunig base. In the presence of two equivalents of NaH, 4,5-diphenylimidazole reacts with benzophenone dichloride in boiling benzene t o give the tetraphenyldiazafulvene ( 1 71, which has already been synthesized by another route [3J, and with 2-methylthio-1,3-dithiolanylium methyl sulfate to form the 6,6-dithiodiazafulvene (18). log E 4.20 3.60 4.12 3.76 4.21 ca. 4 4.52 %position. 2,4-Diphenylpyrrole can be converted into the 0 analog (19) of a sesquifulvalene [m.p. 173 O C ; h:F;"" = 490 nm, log E = 4.64; yield 69 %. Perchlorate: m.p. 306 'C (dec.); = 499 nm, log E = 4.781 by heating in benzene with 4-methylthio-2,6-diphenylpyrylium perchlorate in the presence of one equivalent of NaH. (20) is obtained in the same way from 4,5-diphenylimidazole [m.p. = 227-228 O C ; h;!."" = 550, 518 nm. Perchlorate: m.p. 277 O C (dec.); = 507 nm. Dication: hCH3cN-HC104 max = 450 nm].

Organocatalytic Enantioselective Higher‐Order Cycloadditions of In Situ Generated Amino Isobenzofulvenes

“…In 1968, the first isobenzofulvenes were utilized in cycloadditions by Hafner and Bauer . An amino substituent on the exocyclic carbon atom stabilized the isobenzofulvenes by increasing the aromatic character.…”

The Game of Electrons: Organocatalytic Higher‐Order Cycloadditions Involving Fulvene‐ and Tropone‐Derived Systems

“…This concept was independently elaborated by Jørgensen and co‐workers, who proposed the use of indene‐2‐carbaldehydes 13 as a higherene precursors and presented the first catalytic formation of amino isobenzofulvene systems and transformation of these species via higher‐order cycloaddition with olefins 14 (Scheme ) . Structurally related, achiral amino isobenzofulvenes were previously reported to participate in [10+2]‐cycloadditions with N ‐phenylmaleimide . In Jørgensen's report, the reaction was performed in presence of a C 2 ‐symmetric aminocatalyst 4 b to provide highly peri‐, diastereo‐, and enantioselective formation of chiral benzonorbornene scaffolds 15 .…”

Asymmetric Cross [10+2] Cycloadditions of 2‐Alkylidene‐1‐indanones and Activated Alkenes under Phase‐Transfer Catalysis

“…[5] In 1968, Hafner and Bauer introduced ana mino substituent into the exocyclic carbon to stabilizet he isobenzofulvene species, and accomplished the [10+ +2] cycloadditionr eaction with N-phenylmaleimide (Scheme 1a). [6] In 2017, inspired by this strategy, Jørgensen and co-workers disclosed the first catalytic formation of chiral 8-amino isobenzofulvene intermediates, which facilitated the highly stereoselective [8+ +2] cycloadditions with nitroalkenes to produce complex benzonorbornene architectures, probablyt hrough ac ascade [10+ +4]/3,3-rearrangementp rocess. [7a] They further developed an asymmetric [10+ +4] cycloaddition reaction by employing at ype of newly designede lectron-deficient dienes( Scheme 1b).…”