Iminium chlorides

A representative list of aziridinium salts prepared by reaction of iminium salts with diazomethane is given in Table 9. The reactions of aziridinium salts are many and varied, but will not be given here since their synthetic utility has been explored and reported elsewhere 109,112-114). The products from the reaction of iminium chlorides and diazomethane are reported in Table 10. Many more examples are available in the literature 16). 

The stereoselectivity of the addition of an enamine to an iminium salt is not significantly influenced by its anion. Therefore, iminium chlorides 2a can also be used. Indeed, they are the reagents of choice on large scale syntheses. Compared to iminium chlorides 2a the corresponding tctrachloroaluminates 2b are clearly less hygroscopic and for that reason particularly easy to handle 1. 

Chromium aminocarbenes [39] are readily available from the reaction of K2Cr(CO)5 with iminium chlorides [40] or amides and trimethylsilyl chloride [41]. Those from formamides (H on carbene carbon) readily underwent photoreaction with a variety of imines to produce /J-lactams, while those having R-groups (e.g.,Me) on the carbene carbon produced little or no /J-lactam products [13]. The dibenzylaminocarbene complex underwent reaction with high diastereoselectivity (Table 4). As previously observed, cyclic, optically active imines produced /J-lactams with high enantioselectivity, while acyclic, optically active imines induced little asymmetry. An intramolecular version produced an unusual anti-Bredt lactam rather than the expected /J-lactam (Eq. 8) [44]. 

A development of the reaction described above for the synthesis of pyrrolo[2,l- [l,2,4]triazines using l-aminopyrrole-2-carbonitrile and N,N-dimethyldichloromethyl-iminium chloride utilising ethyl 4-amino-3-cyanopyrazolo[5,1 -c] [ 1,2,4]triazine-8-caiboxylate 60 yields pyrazolo[5,l-c]pyrinudo[4,5-e][l,2,4]triazines 61 <96T3037>. 

Obviously, higher temperatures can lead to faster decomposition. The use of quats above temperatures of 100 to 120 "C usually results in partial or total decomposition. Recently, quats that are stable up to about 200 C have been prepared (Sharma, 1997 Dehmiow, 1993). Figure 3.60 shows two examples. Only the iminium chloride catalyst is also very stable in the presence of hot concentrated NaOH (Dehmiow and Knufinke, 1989). 

Figure 3.60. Quats with high temperature stability a) 4-dialkylaminopyridinium chloride b) bis [tris(dimethylamino)phosphine]iminium chloride.

When l,3r5-triazine is allowed to react with dinitrogen pentoxide and quenched with methanol the cis and trans isomers of 13 3-trinitro-2,4,6-trimethoxy-hexahy drotriazine are obtained. Nitration of the triazine in deuterated nitromethane at -10 °C affords the mixture of cis and trans 2,4,6-trinitrato-l,3,5-trinitro-hexahydro-13,5-triazines which are decomposed at room temperature . Hexahydro-13,5-triaryl-133-triazines cyclorevert upon exposure to HC1 gas to give solid arylmethylene iminium chlorides as new versatile reagents... 

Furthermore, size-exclusion chromatography (SEC) analyses generally reveal a bimodal distribution of molecular weights of the copolymers. Concomitantly, MALDI-ToF mass spectral measurements exhibit two sets of peaks corresponding to copolymer end groups of -OH and -X. For example, utilizing a (salen)CrCl/bis (triphenylphosphme)iminium chloride ([PPNjCl) catalyst for the copolymerization of cyclohexene oxide and carbon dioxide, the two copolymers illustrated in Fig. 6 were observed [26]. 

In the reaction of 4-oxo-6,7,8,9-tetrahydro-4//-pyrido[l,2-a]pyrimidines and phosgene iminium chloride, the 9-substituted pyrido[l,2- ]pyrimidines... 

When tetrahydropyridopyrimidine-3-carboxylate 562 (R = COOEt, R1 = H) was treated with carbon disulfide in the presence of potassium hydroxide at 25-30°C, salt 569 was obtained in good yield (79NEP79/ 3401 82USP4321377). The alkylation of569 with dimethyl sulfate and with ethylene dibromide in ethanol afforded 9-dithioester 570 and 9-(dithiolen-2-ylidene) derivative 571, respectively. When 569 was heated in acetic anhydride for 2 hours, bis product 572 was obtained in 57% yield. 9-Imidazolidine derivative 573 was prepared from both iminium chloride 563 (R = COOEt, R1 = H, R2 = Me) and 9-dithioester 570 by treatment with ethylenediamine (Scheme 37) (79NEP79/3401 82USP4321377 83MIP1). 

Dithiazolium cations can be readily reduced to the stable mono- and diradicals. Reaction of the disalt 43 could be effected, on a milligram scale, by electrolysis in an acetonitrile solution at 50 pA onto Pt wire cathode <1997JA2633>. Larger quantities could be obtained by chemical reduction. Attempts to reduce cation 43 directly with silver or zinc powder were unsuccessful. The most successful approach involved the use of triphenylantimony as reducing agent and bis(triphenylphosphine)iminium chloride ((PPN)Cl Equation (5)). The product obtained (7) is remarkably stable in the solid state, in air, and in organic solutions. 

Enamines have been prepared through reductive-trimethylsilylation of cyanohydrins as precursors of acylsilanes.la 192 As indicated above, these enamines are also excellent starting materials for synthesizing RSMAs via reduction of the corresponding iminium chlorides with sodium borohydride.la,lb... 

It has already been shown that aliphatic acylsilane enamines serve as precursors for RSMA (See Sections III.B.2.i and III.B.2.j) via reduction of their iminium chloride. Transformation of aromatic acylsilane enamines into the corresponding ASMA does not require a reduction step. Their protonolysis leads directly to ASMA, aromatization occurring during the process, sometimes with migration of a silyl group.180... 

A simple route to unsymmetrically substituted 1,2,4,5-tetrazines is the reaction of triethyl orthoformate (or acetate), or DMFDMA, with S-methylisothiocarbonohydrazide salt (9) in the presence of triethylamine and air. The use of iminium chlorides (10) gives similar products. The methylthio group can be readily displaced by nucleophiles to give other substituted tetrazines [94JOC8284],... 

The telluronoamides and telluronohydrazides are stable at 20° in the absence of moisture. Wet solvents or moisture cause elimination of tellurium. The compounds cannot be chromatographed on alumina or silica gel1. The telluronodimethylformamide obtained from cholesteryloxymethylene iminium chloride and sodium hydrogen telluride is a yellow, unstable solid2. 

Dithiazolium cations can be readily reduced to stable radicals. Thus reduction of the disalt 307 by electrolysis or by chemical reduction using triphenylantimony bis(triphenylphosphine)iminium chloride [(PPNC1)] <1997JA2633> gave product 308 which is remarkably stable in the solid state, in air, and in organic solutions. 

Secondary and tertiary enaminones react with formaldehyde and secondary amines as well as with methylene iminium chloride in a Mannich-type reaction with reaction at the -position (equation 165). The use of primary amines leads to pyrimidines.236... 

Another interesting sequence is the amidoselenenation of alkenes for the synthesis of allylic amides. The seleniranium ion is trapped by a nitrile group which is first converted to an iminium chloride and then hydrolyzed to the amide (similar to the Ritter amide synthesis). Several differing nitriles (e.g. methyl to phenyl) have been utilized and all provide good yields of amides. The stereochemistry of addition is always trans but mixtures of regioisomers occur with terminal and unsymmetrically substituted oleflns (equation 24). The -seleno amide is easily converted to the allylic amide by oxidation of the phenyl selenide using the standard conditions. ... 

The acylvanadium complex (78) is converted to the Fischer type (see Fischer-type Carbene Complexes) vanadium complex (79) on treatment with Me3+Bp4 (Scheme 42). The N-substituted carbene analog is formed from Na2[VCp(CO)3] and iminium chloride (80) as shown in... 

Dimethylaminobeiao-l,3-dioxole. Catechol (1) reacts with dimcthylchloro-formiminium chloride in methylene chloride (40°) to give the iminium chloride (2). This is cyclized to the dioxole (3) by treatment with triethylamine in methylene chloride... 

C3H6CI3N phosgene iminium chloride 33842-02-3 25.00 1.3373 2 2074 C3H7N05S DL-cysteic acid 3024-83-7 25.00 1.4330 2... 

This classification is illustrated in Scheme 300. The annelation of o-phenylenediamines with carboxylic acid derivatives is the most common method for the syntheses of benzimidazoles. As discussed in CHEC(1984) and CHEC-II(1996), either Br0nsted or Lewis acids can be used to promote the cyclization (e.g.. Scheme 301 also see Section 4.02.9.1(i)) <1998TA2245>. Carboxylic acids and their derivatives, such as acid chlorides, imidates, and phosgene iminium chloride, have been used in these reactions <2005JME8289, 2006BML4994>. 

Reaction of an Ar,AT-unsubstituted selenourea with chloroacetonitrile in aqueous ethanol affords 2-amino-4,5-dihydro-l,3-selenazol-4-iminium chlorides 35 via selenocarboimidate hydrochlorides. Reaction in anhydrous solvent gave only the selenocarboimidate hydrochlorides, whilst reaction in aqueous ethanol proceeded through to the cyclization step to give 35 (Scheme 13) <2005CL1260>. 

Similarly, reaction with Mdiisopropyl-C-dichloro iminium chloride leads to the formation of the corresponding dimer without the observation of the desired chlorocarbene. 

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