Nitrogen analogues

Intramolecular attack of the carbenes shown in Scheme 30a provides benzo[6]cyclo-hepta[(5 ]-furans and -thiophenes, but the nitrogen analogue (X = NH) yields 9,10-dihydro-acridine 81AJC1037). Photolysis of 2-biphenyl isocyanide (Scheme 30b) (72JOC3571) and thermolysis of 2-biphenylsulfonyl diazomethane (Scheme 30c) (72CC893) also result in ring expansion. 

There are few examples of formation of simple azetidines from [2 + 2] fragments, although this type of approach is important for certain azetidine derivatives, e.g. azetidin-2-ones (see Section 5.09.3). Nitrogen analogues of the Paterno-Buchi route to oxetanes are rare an example involves the photoaddition of 3-ethoxyisoindolone (37) to the enol ether (38) (75JA7288, 72CC1144). 

The term enamitie was first introduced by Wittig and Blumenthal (7) as the nitrogen analogue of the term enol. ... 

A variant of the AFO reaction delivers nitrogen analogues of 3-hydroxyflavonol as described by Schlenoff and coworkers. First methylamino acetophenone (26) is... 

A number of diarylmethyl alkylpiperazines, such as, for example lidoflazine, have found use as coronary vasodilators for the treatment of angina. The most recent of these interestingly incorporates a 2,6-dichloroaniline moiety reminiscent of antiarrhythmic agents. Treatment of the piperazine carboxamide 124 with acetone leads to formation of the nitrogen analogue of an acetal, the aminal 125. Alkylation of the remaining secondary nitrogen with chloroamide 126 leads to the intermediate 127. Exposure to aqueous acid leads to hydrolysis of the aminal function... 

Sulphilimines (the nitrogen analogues of sulphoxides) may also be oxidized using hydrogen peroxide. In this case a sulphoximine (a nitrogen analogue of a sulphone) is produced in good yields, as shown in equation (11). 

Besides the polyether-based polymer electrolytes, the nitrogen analogues (polyimines) were also extensively studied. Various other oxygen-containing... 

Fig. 2.142. Structures of anka pigments and two red nitrogen analogues. Pigments I = anakaflavin, II = monascin, HI = monascorubrin, IV = rubropunctatin, V = monascorubramine, VI = rubrop-unctatamine. Reprinted with permission from S. S. Teng el al. [315].

In the nitrogen analogue of the aldol condensation, nitrosoarenes condense with arylacetonitriles to produce cyanoimines [39]. When two equivalents of the acetonitrile is used, further condensation occurs to form [J-cyanovinylamines (Scheme 5.29) [40],... 

Imines are most conveniently visualized as nitrogen analogues of carbonyl groups, since many of the reactions they undergo are paralleled in aldehyde... 

Just as imines may be viewed as nitrogen analogues of carbonyl compounds, the C=N group may also be viewed as carbonyl-like for interpretation of some of its reactions. For instance, nitriles are readily hydrolysed in acid to give carboxylic acids (see Section 7.6.1). This process begins in a similar manner to hydrolysis of imines. 

There is a distinct relationship between keto-enol tautomerism and the iminium-enamine interconversion it can be seen from the above scheme that enamines are actually nitrogen analogues of enols. Their chemical properties reflect this relationship. It also leads us to another reason why enamine formation is a property of secondary amines, whereas primary amines give imines with aldehydes and ketones (see Section 7.7.1). Enamines from primary amines would undergo rapid conversion into the more stable imine tautomers (compare enol and keto tautomers) this isomerization cannot occur with enamines from secondary amines, and such enamines are, therefore, stable. 

The essential feature of enamines is that they are nitrogen analogues of enols and behave as enolate anions. They effectively mask a carbonyl function while activating the compound towards nucleophilic substitution. 

A series of novel 4-substituted-l,4-dihydroquinolines 140 were prepared and found to exhibit moderate to excellent mammalian topo II inhibitory activity. Among the compounds prepared, in general, the nitrogen analogues are the most active compounds and the sulfur analogue is the least active one. The most potent analogue 140 (X=NH-2-pyridinyl), had a topo II potency nearly equivalent to VP-16, a clinically useful topo II interactive antitumor agent, q. (55) [197]. 

A molecule containing a neutral nitrogen atom with four nonbonding electrons (R-N ). While two of these nonbonding electrons are paired, the other two may have parallel spins (thus, triplet state) or antiparallel spins (singlet state). Nitrenes are the nitrogen analogues of carbenes. 

NITRILE HYDRATASE NITRILE HYDRATASE NITRITE REDUCTASE Nitrogen analogues of carbenes,... 

The nitrogen analogues of the rhodamines based on acridine (3.24) are strongly... 

Synthetic routes to the nitrogen analogues of thiophene-1-oxides and thiophene-1,1-dioxides have been developed. Treatment of thiophene-1-oxide 48 with TsN=IPh gave sulfoximide 49 <99TL3785>, while a similar reaction involving thiophene 50 provided a mixture of thiophene-1-imine 51 and thiophene-1,1-diimine 52 amongst several products <99TL5549>. 

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