Irradiation With Tertiary Amines

INTERMOLECULAR ADDITION REACTIONS 2.1. Direct Irradiation With Tertiary Amines 

The initial step in the addition reactions of arenes and aryl olefins with tertiary amines is electron transfer quenching of the singlet arene or aryl olefin acceptor by a ground state amine donor. The free energy of electron transfer can be calculated using Weller s equation (Eq. I)  

Notes Half-wave oxidaiion potentials for amines and arenes from Ref. IS ind fbr tryl oldlns from Ref. 9. Ionization potentials for amines from Ref. 20c and for arenes ftom Ref 20d, 

4- adduets in the case of benzene and naphthalene. Adduct formation has also been observed in the reactions of singlet 

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Irradiation with Tertiary Amines Irradiation with Secondary Amines Irradiation with Heterocyclic Amines ... 

Irradiation with Tertiary Amines ET-Sensitized Irradiation with Tertiary Amines ET-Sensitized Irradiation with Secondary and Primary Amines Additions of Unactivated Alkenes and FuUerenes... 

Similarly, the stilbene isomers (69) react with tertiary amines by ET followed by proton transfer and coupling, forming 70. " During the irradiation of cA-stilbene in the presence of ethyldiisopropylamine, the fratw-stilbene radical anion, tranr-69, was observed by Raman spectroscopy. " The ET mechanism is also supported by a pronounced dependence of the quantum yields on solvent polarity. 

The photoreactions of the isomeric stilbenes with tertiary amines serve as additional examples of olefins functioning as electron acceptors. The irradiation of fra/w-stilbene in the presence of several amines results in the formation of assorted coupling and disproportionation products compatible with net hydrogen abstraction by the photoexcited olefin [188]. 

Pathway C seemed to be especially attractive, because it should enable addition of acyl anion equivalents to a large number of readily accessible activated carboxylic acids (Figure 3.6.10). Thus diversity in all relevant positions should be readily attainable. High-loaded triphenyl phosphine resin 12 (1.6 mmol g-1) was alkylated with bromoacetonitrile under the action of microwave irradiation yielding phos-phonium salt 13 quantitatively. 13 was converted into stable ylide 14 by treatment with tertiary amine. Carboxylic acids were activated in the presence of N-(3-dimethylaminopropyl)-N -ethylcarbodiimide hydrochloride (EDC) and reacted with 14 yielding acyl cyanophosphoranes 15. The reaction was monitored by ATR-IR coupling yields could be determined by spectrophotometric Fmoc-determination and were 90% for Fmoc-phenylalanine as reference amino acid. 

Protonation is another common reaction in this category and reduction of the acceptor via protonation of the radical anion (e.g. by moisture present in the solvent) is often observed as a side process. It may become the main path either under acidic conditions or if the radical cation of the donor is a good proton donor (Scheme 3). As an example, the 1,2-dihydro derivative is the main product from 1,4-dicyanonaphthalene (DON) when irradiated in the presence of a donor and trifluoroacetic acid [33]. Such a reaction is more important when the radical cation is the proton source. Typically, the irradiation of naphthalene with tertiary amines leads to a mixture of 1,4-dihydro- and 1,2,3,4-tetrahydro-naphthalene, as well as tetrahydrobinaphthyl and l(l-diethylamino)ethyl-l,4-... 

Cm is recovered from irradiated Pu/Al alloys and Am02(Pu02)/Al cermets by dissolution, extraction of plutonium with TBP in n-dodecane, extraction of americium and curium from the aqueous raffinate with 50 percent TBP in kerosene, purification of the americium and curium fraction by extraction with tertiary amines, and separation of americium by precipitation of the double carbonate K5 Am02 (003)3 A high-pressure ion-exchange system for the separation... 

Route (1) is referred to as local excitation and route (2) as CTC excitation. It has been observed that the different routes bring about the polymerization of AN with different kinetic behaviors. A 365-nm light will irradiate the CTC only, and in this case the rate of polymerization for different aromatic tertiary amines descends in the following order ... 

Photolysis of aryl azides in amine solution, with a tertiary amine as cosolvent to promote stabilization of the singlet nitrene, has met with some success. For example, the yield of 2-piperidino-3 W-azepme. obtained by the photolysis of phenyl azide in piperidine, is increased from 35 to 58% in the presence of A A /V. /V -tetramethylethylenediamine (TMLDA).180 Also, an improved yield (36 to 60 %) of A,(V-diethyl-3W-azepin-2-amine (38, R = Et) can be obtained by irradiating phenyl azide in triethylamine, rather than in dicthylaminc, solution.181 Photolysis (or thermolysis) of phenyl azide in TMEDA produces, in each case, 38 (R = Et) in 40% yield.181 In contrast, irradiation of phenyl azide in aniline with trimethylamine as cosolvent furnishes jV-phenyl-377-azepin-2-amine (32, R = Ph) in only low yield (2%).35... 

This is the most common method for the preparation of enamines and usually takes place when an aldehyde or ketone containing an a hydrogen is treated with a secondary amine. The water is usually removed azeotropically or with a drying agent, but molecular sieves can also be used. Stable primary enamines have also been prepared.Enamino-ketones have been prepared from diketones and secondary amines using microwave irradiation on silica gel. ° Secondary amine perchlorates react with aldehydes and ketones to give iminium salts (2, p. 1178). Tertiary amines can only give salts (12). 

The Sn2 reaction of triphenylphosphine with triethylbenzylammonium chloride (the tertiary amine is thus the leaving group) was studied under solvent-free microwave conditions. The reaction occurred only under the action of MW [83] irradiation (Eq. 53). 

The importance of tertiary amines in the photochemically induced electron transfer reactions has also been addressed5. Direct irradiation of aromatic or aliphatic amines often leads to the scission of C—N, N—H or C—H bonds that lead to the subsequent chemical reactions by radical pathways6. In this section, photochemical reactions of amines reported since 1978 will be considered with emphasis on photoinduced electron transfer. Photochemical reactions of inorganic and organometallic compounds will not be included unless photochemistry of amine moieties is the primary interest. 

A different mode of reaction, however, is observed in photoreductions of nitroaromatics by aromatic tertiary amines. Irradiation of benzene solutions of N-methylated anilines and either m-chloronitrobenzene or 1-nitronaphthalene results in oxidative demethylation of the amines accompanied with reduction of the nitro compound to the corresponding arylamine 49). The authors suggest that hydrogen abstraction from the methyl group takes place as the primary chemical event. 

Interestingly, the alkene to allene conversion can be carried out directly without isolation of the intermediate dihalocyclopropane. This process involves the treatment of the alkene with 1 equiv. of carbon tetrabromide and 2 equiv. of methyllithium in ether at -65 °C.163 Ultrasonic irradiation facilitates the formation of cyclopropylidenes, and therefore the allenes, from dihalocyclopropanes under the influence of Li, Na or Mg.1 The reactions are usually complete in 5-15 min. A report165 on the use of n-butyllithium complexed with the chiral tertiary amine (-)-sparteine, leading to optically active allenes, seems to be of questionable value. 

The radical anion Cw, can also be easily obtained by photoinduced electron transfer from various strong electron donors such as tertiary amines, fer-rocenes, tetrathiafulvalenes, thiophenes, etc. In homogeneous systems back-electron transfer to the reactant pair plays a dominant role resulting in a extremely short lifetime of Qo. In these cases no net formation of Qo is observed. These problems were circumvented by Fukuzumi et al. by using NADH analogues as electron donors [154,155], In these cases selective one-electron reduction of C6o to Qo takes place by the irradiation of C6o with a Xe lamp (X > 540 nm) in a deaerated benzonitrile solution upon the addition of 1-benzyl-1,4-dihydronicoti-namide (BNAH) or the corresponding dimer [(BNA)2] (Scheme 15) [154], The formation of C60 is confirmed by the observation of the absorption band at 1080 nm in the near infrared (NIR) spectrum assigned to the fullerene radical cation. 

The photochemical reaction of tertiary amines with C6o can be used to synthesize alkaloid-C6o derivatives [269], Irradiation of alkaloids bearing a tertiary amino group such as tazettine, gramine, scandine, or 10-hydroxyscandine with C6o led to the isolation of alkaloid-C6o adducts. Use of tazettine and gramine in the reaction yielded the expected [6,6] adduct. In addition to the pyrrolidinofullerene 94a-b, a new type of monoadduct 95a-b with a bis-[6,6] closed structure characterized by UV-vis, FT-IR, II-NMR, 13C-NMR, II- II-COSY, ROESY, HMQC, and HMBC spectroscopy was obtained from the reaction with scandine 93a and its 10-hydroxy derivative 93b (Scheme 38). 

The irradiation of chloro- or cyanosubstituted aromatic acceptors in the presence of tertiary amines give rise to (net) substitution products. In analogy to the coupling reactions of these acceptors with alkenes (Sect. 4.1) an addition-elimination... 

Under irradiation with light (A > 290 nm), tertiary amines are able to transfer one of the electrons of the lone pair on nitrogen to a molecule to produce a cation radical that loses a proton a- to nitrogen to form an a-amino radical.280... 

Ju and Varma envisioned that the nucleophilic substitution reaction of alkyl halides with amines may be accelerated by microwave energy because of their polar nature [88]. An environmentally friendly synthesis of tertiary amines via direct JV-alkylation of primary and secondary amines by alkyl halides under microwave irradiation was developed (Scheme 21), that pro-... 

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