Imino functionalities

Iminopenicillanic acid derivatives have been particularly useful in the preparation of 6a-methoxypenicillanates (note that the 6-diazo group is a special case of the 6-imino function, and that a 6-acyliminopenicillanate was obtained from the 6-keto derivative in Scheme 37). 

Heating the 5-isocyano-l,3,4-thiadiazolo[3,2- ]pyrimidin-5-one 115 with 10% hydrochloric acid gave a mixture of the 5-imino-l,3,4-thiadiazolo[3,2- ]pyrimidin-7-one 116 (10%) and the l,2,4-triazolo[l,5-c]pyrimidine-5,7-dione 117 (35%) (91JHC489). Formation of 117 probably occurred through thiadiazole ring rupture of 116 and recyclizatioii with its imino function together with desulfurization (Scheme 43). 

The oxo function in the 2-aminobenzophenone can also be masked as an imino function,31 32 an example being the reaction of 10. 

In the case of 2-(2-hydroxyethyl)piperidine it is not necessary to protect the NH group because of steric hindrance at this position. The imino function within the pyridinoindole is not nucleophilic enough to react with CDI. 

Molecules containing the imino function are commonly reduced to hydro-dimeric products when irradiated in isopropyl alcohol, as illustrated in (4.1) 401 and (4.2) 402). The photoreduction of nitrogen containing heterocycles has been reviewed recently 403). 

For 340a and 341a, another dynamic process was also frozen out. This process must be due to nitrogen inversion in the imino function, which results in E/Z isomerization (93MI2). This inversion could occur via amino-imino tautomerism (91JOC3194). The E and Z isomers are practically equally stable since there is no noteworthy steric hindrance in either form. 

Thus far we have seen that Schiff base ligands tend to promote six-coordination, but an unusual reaction has been found to occur between TiCl2(salen) and borohydride. No reduction at titanium is seen, but rather, addition of BtLr to the imino function of the ligand occurs to give a dimeric seven-coordinate titanium(IV) compound, (24), containing amine-boranes as... 

Fused pyrroles have been prepared by the condensation of an amino group with a suitably positioned carbonyl function. Thus, reduction of ethyl (3-nitro-2-thienyl)pyruvate (226) with tin(IV) chloride gave 5-ethoxycarbonyl thieno[3,2-6]pyrrole (47), by the spontaneous cyclization of the intermediate amino derivative (227 Scheme 76) (64JOC2160). The formation of indolo[3,2-6]indole (229), a dibenzannelated pyrrolopyrrole, by the cyclization of (228) with tin(IV) chloride (Scheme 77) is an example of a case where reduction of the imino function in the starting material is necessary before cyclization will occur (78AHC(22)183). 

These potential ligands are of interest since they contain both oximinato and imino functions. 

Five-membered ring heterocyclic azides are readily reduced (H2S, LiAlH4) to the corresponding amines. On thermolysis they lose nitrogen, thereby generating nitrenes. For example, 3-azido-2-vinyl derivatives in xylene at 120130C yield [3,2-A]-fused pyrroles 430 nitrene insertion into an ortho-disposed imino function similarly yields [3,2-A]-fused pyrazoles 431. 

Dicarbonyl 39 is quite effective in promoting the reductive coupling of carbonyl or imino functional groups. Addition of diethyl ketomalonate to solutions of 39 yields 43 (116). 

The codimerization of two different phosphaalkynes is realized in the reaction between the r -phosphaalkyne complex 114 and i-Pr(Me3Si) N—C=P. The preparation of 115 is accompanied by Me3SiCl elimination and the formation of an exocyclic imino function see Eq. (23).56c... 

The reaction mechanism is presumed to rely on the ability of the a,/3-unsaturated acyl 151 to generate an cr-ketenyl radical 152, which reacted as an electrophile toward the imino functionality to produce the radical-zwitterion 153 (Scheme 63 <2003JA5632>). 

In order to prevent enamination, different strategies can be employed. The easiest way is to eliminate the extra CH unit that causes enamination in the first place. To this effect, imino functionalised imidazolium salts were developed that have the imino functionality directly attached to the imidazole ring of the NHC unit (see Figure 3.37). 

Although the hemilabile behaviour of the imino functional group together with an apparent isomerisation process on palladium may make it difficult to achieve high chiral resolution (ee) in asymmetric catalysis. Bonnet and Douthwaite developed an imino functionalised carbene ligand system based on the diamino cyclohexane framework that has achieved ees of up to 92% in palladium catalysed allylic alkylatiou reactions using ( )-l,3-diphenylprop-... 

Unsaturaled systems substituted with a fluoroalkyl group more readily undergo [4-I-2] than [2-f2] cycloaddition reactions (sec Section 2.1.1.6.2.1.1.). This preference has resulted in relatively few reported examples of [2-1-2] cycloaddition reactions to give four-membered rings. Most applications concern heterocycloaddition reactions involving fluoroalkyl ketonic and imino functions. 

Of particular interest in the latter case is the use of N-NMR spectroscopy for the determination of J( P, N) data, of which there are few examples for systems having two coordinate sp -hybridised nitrogen linked to phosphorus. " Various acyclic bis(aminophosphines) have also been reported, including the imino-functional system (96), the bis(phosphino)-hydrazines (97) and -ureas (98), and the l,8-bis[bis(dialkylamino)phosphino]naphthalenes (99). There has also been significant activity in the synthesis of cyclic aminophosphines. An improved route to the four-membered ring system (100) is afforded by the reaction of phosphorus trichloride with t-butylamine in a 1 3 mole ratio in THF. Treatment of this with ammonia in THF/triethylamine at — 78°C gives (101),... 

Interconversion of an imino functional group into an amino moiety by hydrolysis is part of those aminocyclopropane syntheses in which an imino, imidato, thioimidato or amidino... 

Cycloaddition of nitrone (415b) to the imino function in 414 gave aminocyclopropanes 417 or 418 as well as other products (equation 103). The expected, primary product, 416, was obtained from a nitrile ylide (415a) by a cycloaddition reaction. ... 

The C-3 carbon atom undergoing hydroxylation is a to both a lactam carbonyl and an imino functionality. 

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