Irradiation yields

Similarly, photooxidation of dihydrocoralyne (108) in hot methanol at pH 8, subsequent addition of sodium methoxide and additional irradiation yielded 6,7-dimethoxyisoquinolone and 3-methyl-3,5,6-trimetho-xyphthalide via the betainic intermediate 109 (77H45) (Scheme 39). It was demonstrated earlier that dihydrocoralyne is oxidized to this betaine in quantitative yields under physiological conditions (76H153). The autoox-idative degradation of the mesomeric betaine was rationalized by the addition of singlet oxygen. 

We entered this field when we studied the photoisomerization of simply substituted nitrile oxides 138 (R = Cl, Br, CN).188 Matrix irradiation yields the corresponding isocyanates 144. In the case of chloronitrile oxide besides the absorptions of chloroisocyanate189 the bands of chloronitrene190 also appear. It can be assumed that the nitrile oxide-isocyanate rearrangement starts with the ring closure 138 - 140.191192... 

The TV-protected nitrosoimidazole carbonitrile 42 - which can easily be obtained from the commercially available 4-nitroimidazole in 4 reaction steps - was treated with phenyl methylcarbazate 43 to give a substituted triazenyli-midazole 44. The cyano group of this compound was first hydrolyzed to an amide function to produce 45, and then irradiation yielded the end product 9a in high yield (79%). 

In attempts to cany out cyclisation from butadiene 1,3 in the gaseous phase and under photochemical conditions R Srinivasan (J.Amer.Chem.Soc. 88, 3765 (1966) showed that irradiation yields a complex mixture of ethylene, acetylene, but-1 ene, hydrogen and polymers. The quantum yields of acetylene and ethylene formation increase with pressure. 

In one approach, polymethacrylate-type monoliths have been fabricated by copolymerization of the chiral monomer 0-9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 1 or 0-9-(tert-butylcarbamoyl)-ll-[2-(methacryloyloxy) ethylthio]-10,ll-dihydroquinine 2 (see Figure 1.34a), the comonomer 2-hydroxyethylmethacrylate (HEMA), the crosslinker ethylenedimethacrylate (EDMA) in presence of the binary porogenic solvent mixture cyclohexanol and 1-dodecanol, directly in a single step within fused-silica capillaries. Initiation of the polymerization by either thermal treatment or UV irradiation yielded microglobular polymer morphologies, such as those well known from their corresponding nonchiral... 

Henglein [71] has used pulsed ultrasound and has shown that the degree of polymerisation decreases when the duration of pulsed ultrasound is decreased. The growth and collapse of cavitation bubbles require a finite time - they are not instantaneous. Henglein has also shown that the rate (and degree of polymerisation) depends upon the nature of the gas used to saturate the system. For the polymerisation ofmethacrylic acid in aqueous solution, a 15 min irradiation yielded 10.7% conversion in the presence of Nj, 1.8% conversion in the presence of O2 (low presumably due to inhibition) and no polymerisation in a degassed solution). 

Aminopyrazoles and other aminoazoles having CH-nucleophilic center in MCRs with Meldrum s acids and aldehydes in boiling primary alcohols, DMF, or nitrobenezene [119, 120] as well as in glycol [121] or in water [100] under microwave irradiation yielded exclusively azolopyrimidineones of type 87 (Scheme 37). 

Electrophilic trifluoromethylation is still of minor importance in synthetic applications. The limited efficiency and the cost of the reagents able to transfer a CF3 cation are important obstacles for the development of this approach. However, CF3-S" -type reagents can react with activated enolates under Lewis acid catalysis. A recent and promising result shows that, when the reaction is performed under UV irradiation, yields significantly increase. This can lead to synthetic applications, as exemplified by the recent preparation of 7-CF3 steroids (Figure 2.37). ... 

Fig. 24. The yield of UpU and UpC as functions of dose at 280 nm. The photo-products were separated by electrophoresis 24 hr after the end of the irradiation. Yields are given as a percentage of CpC (Freeman, Hariharan, and Johns71).

Photochemical decomposition of trifluoromethanethiol (F3CSH) on irradiation yields hydrogen, sulfur, fluoroform, XLIX, and XLVII, by... 

Complexes of 98a-d have been prepared with optically active 3, also [56, 152, 154, 303]. Their irradiation yields only 99 as photoproducts, as before, but in many cases they have a large enantiomeric excess. The data are summarized in Table 14. 

The first synthesis of the unstable pyrido[2,1 -ajisoindole system has been achieved by a cyclization of this type A-benzyl-2-bromo-pyridinium salts (336) on irradiation yield the pyrido[2,l-a]iso-... 

The Leuckart reductive animation of carbonyl compounds with ammonium formate or formamide was found to benefit strongly, when the reaction was carried out under solvent free conditions with microwave irradiation. Yields of N-alkylated formamides of up to 97% were produced in reaction times of about 30 min, as compared to thermal... 

Decomposition of a different type is observed on irradiation of the 3-thiazoline-2-thione (225) resulting in loss of sulfur and the formation of the vinyl isothiocyanate (226)181 further irradiation yields the isoquinoline-1-thione (227). 

The normally sluggish Diels-Alder cycloaddition between cyclohexa-1,3-diene and various enones and enals can be activated by precoordination of the diene to a jt-basic molybdenum complex TpMo(NO)MeIm(//-cyclohexadiene)].134 The 4-1-2-cycloaddition of cyclohexa-2,4-dienones with electron-deficient 2n -dienophiles produced bridged bicyclo[2.2.2]octenones. Triplet-sensitized irradiation of these bridged bicyclooctenones produced bicyclo[3.3.0]octanoids, whereas direct irradiation yielded bicyclo[4.2.0]octanes.135... 

Mattay et al., having discovered exciplex emission from solutions of benzene and 1,3-dioxole [122], continued their investigations with a study on selectivity and charge transfer in photoreactions of a,a,a-trifluorotoluene with 1,3-dioxole and some of its derivatives, and with vinylene carbonate and dimethylvinylene carbonate [15,143,144], a,a,a-Trifluorotoluene and 1,3-dioxole upon irradiation yield three types of products ortho cycloadducts, meta cycloadducts, and so-called substitution products (Scheme 44). The products are formed in the ratio ortho adductsimeta adducts substitution products = 0.8 1.7 0.3. The substitution reaction (which is really an addition of a C—F bond to the double bond of 1,3-dioxole, but named substitution in order to distinguish it from the ortho addition [186] is supposed to start with electron transfer from 1,3-dioxole to excited a,a,a-trifluorotoluene. The radical anion then releases a fluoride ion, which adds to the 1,3-dioxole radical cation. Radical combination then leads to the product. 

Hasegawa et al. reported another example of a [2 + 2] asymmetric transformation in a chiral crystal. [16] Ethyl 4-[2-(pyridyl)ethenyl] cinnamate 15 crystallizes in a chiral space group Phhh and upon irradiation yields a chiral dimer 16 with 92-95% ee. 

However, while 313 and 366 nm direct irradiation yields a cis- trans quantum yield of-0.005, the benzophenone triplet sensitized and the low energy direct irradiation yield is only —0.001. These results support the notion that two reactive excited states are involved one associated with the styrylferrocene which leads to the more efficient isomerization and a ferrocene-type excited state at lower energy which has a smaller tendency to undergo cis -trans isomerization. It is interesting to note that the 100% trans photostationary state is likely very close to the amount expected at thermal equilibrium. Such a result would be consistent with an intramolecular CT transition to yield a radical-anion ferricinium complex as in reaction (47). The radical anion could yield cis trans isomerization just as in the Ru(II)-styrylpyridine complexes. The wavelength dependence of the isomerization of the styrylferrocene is consistent with (47) in that upper excited states are required for the photooxidation of ferrocene to ferricinium in CC14.135 ... 

The insertion of a one-carbon unit into a /3-formylenamide under microwave irradiation yields the pyridine (Equation 89) <2004SL1309>. 

The insulin receptor is present in trace amounts in the plasma membrane of liver cells. Using radiolabeled arylazido derivatives of insulin, which on irradiation yield reactive nitrenes, components of the receptor with molecular weights of 135,000 and 90,000 daltons have been identified (Jacobs etal., 1979 Yip etal., 1980 Wisher etal., 1980). The identity of the two polypeptides has been confirmed by chemical crosslinking to radiolabeled insulin and by purification of the receptor by affinity chromatography. 

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. 

Phenol can be nitrated upon nitrate irradiation, yielding 2- and 4-nitrophenol [54,58,79,99,100]. The generation of OH + NO2 upon nitrate photolysis (reactions 1 and 2) would suggest the possibility that phenol nitration might follow an OH-mediated pathway as in the gas phase [80,81]. Furthermore, hydroxyl-mediated nitration in aqueous solution has been described in the case of benzene [107]. However, the addition of hydroxyl scavengers to the system (formate [79], 2-propanol [58]) favours the formation of ni-trophenols, while an OH-mediated nitration would be inhibited by hydroxyl consumption. The positive effect of the scavengers can be accounted for in the hypothesis that phenol nitration takes place upon reaction with nitrogen... 

Analogue of VITD-R agonist 1,25-Dihydroxyvitamin D3 Deglycosylation yields VITD-R agonist 1,25-Dihydroxyvitamin D ) [excess calcinogenic —> pathological Ca-+ deposition] UV irradiation yields Vitamin D- [indicator of plant product fungal contamination]... 

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