Aryl diimides

Protonation of the anion [SN2] by acetic acid in diethyl ether produces the thermally unstable sulfur diimide S(NH)2. Like all sulfur diimides, the parent compound S(NH)2 can exist as three isomers (Scheme 5.5). Ab initio molecular orbital calculations indicate that the (cis,cis) configuration is somewhat more stable than the (cis,trans) isomer, while the (trans,trans) isomer is expected to possess considerably higher energy. The alternative syn,anti or E,Z nomenclatures may also be used to describe these isomers. The structures of organic derivatives S(NR)2 (R = alkyl, aryl) are discussed in Section 10.4.2. 

Salts of mono-alkylated or arylated sulfur diimide anion [RNSN] (R = aryl, Bu, SiMcs) are prepared by Si-N cleavage of RNSNSiMcs with [(Me2N)3S][Mc3SiF2]. ° ° These anions adopt cis configurations with very short terminal S-N bond lengths (1.44 - 1.49 A) indicative of a thiazylamide anion, [RNS N] (5.21). ... 

Dimerization. One of the principal reactions of NH is dimerization to diimide (N2H2). Azobenzenes are often obtained in reactions where aryl nitrenes are... 

Figure 11.1 General structure of pyromellitic diimides, naphthalenediimide, and perylenediimide compounds (R = aryl, alkyl).

Baylis-Hillman adducts such as 55 and 56 derived from 2-nitrobenzaldehydes were shown to function as useful precursors to functionalized (1H)-quinol-2-ones and quinolines. Treatment of 55 and 56 with iron and acetic acid at 110 °C afforded 57 and 58, respectively <02T3693>. A variety of other cyclization reactions utilized in the preparation of the quinoline scaffold were also reported. An iridium-catalyzed oxidative cyclization of 3-(2-aminophenyl)propanols afforded 1,2,3,4-tetrahydroquinolines <02OL2691>. The intramolecular cyclization of aryl radicals to prepare pyrrolo[3,2-c]quinolines was studied <02T1453>. Additionally, photocyclization reactions of /rans-o-aminocinnamoyl derivatives were reported to provide 2-quinolones and quinolines <02JHC61>. Enolizable quinone and mono- and diimide intermediates were shown to provide quinolines via a thermal 6jt-electrocyclization <02OL4265>. Quinoline derivatives were also prepared from nitrogen-tethered 2-methoxyphenols. The corresponding 2-methoxyphenols were subjected to a iodine(III)-mediated acetoxylation which was followed by an intramolecular Michael addition to afford the quinoline OAc O... 

Ac, acetyl AIBN, azobis(isobutanonitrile) All, allyl AR, aryl Bn, benzyl f-BOC, ferf-butoxycarbonyl Bu, Butyl Bz, benzoyl CAN, ceric ammonium nitrate Cbz, benzyloxycarbonyl m-CPBA, m-chloroperoxybenzoic acid DAST, diethylaminosulfur trifluoride DBU, l,8-diazabicyclo[5.4.0]undec-7-ene DCC, /V. /V - d i eye I oh e x y I c ar bo -diimide DCM, dichloromethyl DCMME, dichloromethyl methyl ether DDQ, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone DEAD, diethyl azodicarboxylate l-(+)-DET, L-(+)-diethyl tartrate l-DIPT, L-diisopropyl tartrate d-DIPT, D-diisopropyl tartrate DMAP, 4-dimethylaminopyridine DME, 1,2-dimethoxyethane DMF, /V./V-dimethylformamide DMP, 2,2-dimethoxypropane Et, ethyl Im, imidazole KHMDS, potassium hexamethyldisilazane Me, methyl Me2SO, dimethyl sulfoxide MOM, methoxymethyl MOMC1, methoxymethyl chloride Ms, methylsulfonyl MS, molecular sieves NBS, N-bromosuccinimide NIS, /V-iodosuccinimide NMO, /V-methylmorpho-line N-oxide PCC, pyridinium chlorochromate Ph, phenyl PMB, / -methoxvbenzyl PPTs, pyridiniump-toluenesulfonate i-Pr, isopropyl Py, pyridine rt, room temperature TBAF, tetrabutylammonium fluoride TBS, ferf-butyl dimethylsilyl TBDMSC1, f-butylchlorodimethylsilane Tf, trifhioromethylsulfonyl Tf20, trifluoromethylsulfonic anhydride TFA, trifluoroacetic acid THF, tetrahydrofuran TMS, trimethylsilyl TPAP, tetra-n-propylammonium perruthenate / -TsOH. / -toluenesulfonic acid... 

Carbodiimides are a unique class of reactive organic compounds having the heterocumu-lene structure R—N=C=N—R. They can be formally considered to be the diimides of carbon dioxide or the anhydrides of 1,3-substituted ureas, and they are closely related to the monoimides of carbon dioxide, the isocyanates. The substituent R can be alkyl, aryl, acyl, aroyl, imidoyl or sulfonyl, but nitrogen, silicon, phosphorous and metal substituted carbodiimides are also known. The unsubstituted carbodiimide HN=C=NH is isomeric with cyanamide, H2NCN. Mono substituted carbodiimides, generated in the thermolysis of 1-substituted tetrazoles, can be isolated at liquid nitrogen temperature but isomerize to the cyanamides at higher temperatures. ... 

Also, highly fluorescent N-alkyl- or N-aryl-N -[4-(5-phenyloxazol-2-yl)benzyl]carbo-diimides 10 are prepared from the corresponding thioureas 9 and HgO. ... 

Thiophene-2,5-bis-iminophosphoranes are converted to the corresponding bis-carbo-diimides using aryl isocyanates but the bis-carbodiimides were converted in solution to the corresponding bis-guanidines. ... 

The parent compound is the highly reactive diimide, HN=NH, which at room temperature exists only as a short lived intermediate, though recently it has been obtained as a yellow solid at liquid air temperature. The aromatic and aliphatic azocompounds are then derived by substituting aryl or alkyl radicals for the hydrogen atoms. 

A-Aroyl-5,5-dialkylsulfur diimides (218), prepared by aroylation of 5, 5 -dialkylsulfur diimides, in which the halogen of the aryl halide is activated towards nucleophilic substitution by the />-nitro group, undergo base-catalysed cyclization with sodium methoxide in dimethylformamide to yield 6-nitro-2,2-dialkyl-2A, l,3-benzothiadiazin-4-ones (219) in 73-88% yield (Equation (27)) <84CB2779>. 

Levchenko and Balon" have examined the regiochemistry of cycloaddition of several symmetrical bis(aryl)sulfonyl sulfur diimides with ( )-piperylene and isoprene which afforded the C-3 and C-5 substituted adducts, respectively (Scheme l-III). These results were confirmed by Wucherpfennig and Kresze, who also found that chloroprene gave the 5-substituted product. ... 

Adducts of unsymmetrical sulfur diimides, in which the nitrogen atom in the heterocyclic ring bears an aryl substituent, undergo acidic hydrolysis to produce Af-aryl-substituted homoallylic amines (Scheme 1-XII). Alkaline hydrolysis of these adducts leads to A(-arylpyrroles, similar to the reaction shown in Eq. (21). ... 

With respect to the substrate scope, ketones are the most efficient nucleophiles although the intermolecular reaction works also well for esters, amides and Weinreb amides (Fig. 2.7). Regarding the Michael acceptor, enones are the best electrophiles with a wide range of substituents tolerated (alkyl, aryl and heteroaryl ketones). a,p-Unsaturated esters, in the case of the intermolecular cyclopropanation, and a,p-unsaturated diimides for the intramolecular reaction, extends the substrate scope of the process (Fig. 2.7). A transition state model for the intramolecular cyclopropanation reaction has been proposed as depicted in Scheme 2.38 for catalyst 65 [106d]. In this model the ammonium salt adopts a conformation that gives the Z-enolate of the nucleophile on deprotonation with the base. The intramolecular conjugate addition of the enolate then takes place through a boat-type transition state. 

Khorana [43,45] has studied a very limited number of examples and noted absorption at 2150 cm" A more detailed study of both frequency and intensity has been made by Meakins and Moss [44]. Nine carbodiimides were examined by these authors, and all showed a very intense absorption in the range 2152—2128 cm" accompanied in three instances by a much weaker combination band at lower frequencies. Little frequency or intensity differences was found between alkyl and aryl derivatives. The intensity of the band was assessed by a variety of methods, and the extinction coefficient e was of the order of 1400. This is some IV2 times as strong as a normal ketonic carbonyl absorption. Mogul [60] has reviewed the infra-red and Raman spectra of carbodiimides. The findings confirm those of Meakins, and others in the infra-red, but add the additional observation that the band doubles when an aromatic ring is directly attached to the diimide group. In the Raman spectra the symmetric vibration is of course the more intense and this occurs near 1460 cm" ... 

R = aryl Sulfur diimide Sulfur diimide (0.5 eq.), acetonitrile, reflux 95 [51]... 

---