Reactions N-substituted

Tu, Li, and coworkers also developed a new allylic functionalization without the use of metal catalysts [59-61]. Efficient annulation of enaminones 57 with arylglyoxal monohydrates 58 and the subsequent allylic functionalization with aliphatic carboxylic acids 38 as nucleophile reagents provided multifunctionalized indoles 98 with 75-89% yields (Scheme 12.38) [59]. To further explore the scope of this domino reaction, N-substituted 3-aminocyclohex-2-enones were employed. Interestingly, two molecules of arylglyoxal mono hydrate and N-substituted... 

The best method of preparing hydrazides is by the reaction of hydrazines with esters. Acyl halides and amides may also be reacted with hydrazines. In the case of the Ing-Manske reaction, N-substituted phythalimides are reacted with hydrazine to generate a primary amine and the cyclic phthalhydrazide. 

The independent preparation of potassium phthabmide (from a solution of phthalimide in absolute ethanol and potassium hydroxide in 75 per cent, ethanol) may be avoided in many cases by boiling phthalimide with the halide in the presence of anhydrous potassium carbonate. The N-substituted phthalimide (I) is frequently cleav with difficulty this is often facilitated by reaction with hydrazine hydrate to give an intermediate product, which is easily decomposed by hydrochloric acid to 3deld the insoluble hydrazide of phthaUc acid (II) and the primary amine (III) ... 

A very mild and efficient synthesis of N-substituted -lactams uses the Mitsunobu reaction (see section 2.6.2) for the ring closure of seryl dipeptides protected at the terminal N as 4,5-diphenyloxazol-2(3f/)-one ( Ox ) derivatives (see section 2,6.3)... 

Maleic anhydride condenses with 2-aminothiazole-4-carboxylic acid giving the raaleimide 107 (269) another report claims, however, that the reaction of 2-amino-4-methylthiazole with this anhydride gives the N-substituted maleamic acid (108) (Scheme 73) (270). 

A-4-Thiazoline-2-thiones can be obtained directly from 2-thiazolyldiazonium tetrafiuoroborate by reaction with an excess of thiourea (9). When 1 1 stoichiometry is used, the adduct (7) can be isolated. Further treatment of 7 with an excess of thiourea leads to the 2-mercaptolhiazole (3) 9). 2-Iminothiazoles 81 when heated at 150°C with CSt sive N-substituted A-4-thiazofine-2-thiones (9) (Scheme 31... 

Reaction takes place on nitrogen when the electrophilic center is an sp carbon, particularly if it is charged. Thus Mannich reaction yields the N-substituted compound (71 and 72) (Scheme 34) (54. 157-159). The same reaction is reported with piperidine, o-toluidine. and methylaniline (158). 

Acrylonitrile reacts with the sodium salt of 4.5-dimethvl-A-4-thiazoline-2-thione (73J (R4 = R5 = Me) to yield 3-(2-cyanoethyl)-4.5-dimethyl-A-4-thiazoline-2-thione (74) (R4 = R, = Me) (Scheme 35 (160). Humphlett s studies of this reaction showed that the size of the R4 substituent is a determinant factor for the S versus N ratio (161. 162). If R4 == H, 100% of the N-substituted product (74) is obtained this drops to 50% when R4 = methyl, and only the S-substituted product (75) is obtained when R4 = phenyl. The same trend is observed with various CH2 = CH-X (X = C00CH3. COCH3) reagents (149). The S/N ratio also depends on the electrophilic center for CH2 = CH-X systems thus S-reaction occurs predominantly with acrylonitrile, whereas N-substitution predominates with methvlvinvlketone (149). 

Alkylation by diazoalkanes gives more N-substituted product when the reaction goes through an S l transition state. Representative data are given in Table Vll-lOa. and they are discussed in Ref. 101. 

Alkylation of A-4-thiazoline-2-one may yield O-R or N-R derivatives according to experimental conditions. With diazomethane in ethanol O-raethylation takes place (29. 36. 214). N-Methylation is reported when a basic solution of A-4-thiazoline-2-one reacts with methyl iodide or dimethylsulfate (21, 29, 215, 216), Reaction of l-chloro-2-dimethyl-aminoethane with the sodium salt of 4 R-A-4-thiazoline-2-one (91) in alcohol, first claimed to yield the aminoalkylether (217, 218), was shown after infrared investigation to give the N-substituted derivative (92) (107), even when R Ph (Scheme 45). More probably the site of reaction in... 

N-substituted selenoureas give the same condensation reaction (Scheme 9. Table X-3). 

II. Thiazoles from a-Halocarbonyl Compounds and Derivatives 211 2. Reaction with N>Substituted Thioamides (ThiazoHum Salts)... 

Thiazolium salts with alkyl (103, 722), arylalkyl (116), aryl (305), or heteroaryl (96) substituents on the nitrogen have been also prepared by this procedure. As in the thiazole series, N-substituted thioamides can be formed directly in the reaction mixture from phosphorus pentasulfide and N-substituted amides (127). These methods are important in the synthesis of thiamine 102 (vitamin Bj) (Scheme 45). 

Preparation from Amines. The most common method of preparing isocyanates, even on a commercial scale, involves the reaction of phosgene [75-44-5] and aromatic or aUphatic amine precursors. The initial reaction step, the formation of N-substituted carbamoyl chloride (1), is highly exothermic and is succeeded by hydrogen chloride elimination which takes place at elevated temperatures. 

A number of other N-substituted 2-pyrroHdinones have been offered commercially or promoted as developmental products. These materials offer different and sometimes unique solvency properties. AH are prepared by reaction of butyrolactone with suitable primary amines. Principal examples are Hsted in Table 4. 

Acylation of pyridazinones and related compounds in the presence of weakly basic catalysts such as pyridine or sodium acetate produces IV-acylated products, while O-acylated products are obtained under strongly basic conditions. However, the reaction between 6-chloropyridazin-3(2//)-one with chlorocarbonates and that of maleic hydrazide with unsaturated acid chlorides or chloromethylsulfonyl chloride gives preferentially N-substituted products. 

Mannich reaction with pyridazinone 1-oxides takes place at the a- or y-positions relative to the iV-oxide group, in contrast to the reaction in the pyridazinone series, where N-substituted products are formed. Pyridazin-3(2FT)-one 1-oxide gives first the corresponding 6-substituted derivative with excess of the reagents, 4,6-disubstituted products are obtained. When position 6 is blocked the corresponding 4-dialkylaminomethyl derivatives are obtained. 

Phase transfer catalysis has been used with success to prepare N- substituted pyrazoles (78MI40403, 79MI40408, 70JHC1237, 80JOC3172) and this procedure can be considered the simplest and most efficient way to obtain these compounds. Experimental design methodology has been used to study the influence of the factors on the reaction between pyrazole and -butyl bromide under phase transfer conditions (79MI40408). 

Schmidt reaction of ketones, 7, 530 from thienylnitrenes, 4, 820 tautomers, 7, 492 thermal reactions, 7, 503 transition metal complexes reactivity, 7, 28 tungsten complexes, 7, 523 UV spectra, 7, 501 X-ray analysis, 7, 494 1 H-Azepines conformation, 7, 492 cycloaddition reactions, 7, 520, 522 dimerization, 7, 508 H NMR, 7, 495 isomerization, 7, 519 metal complexes, 7, 512 photoaddition reactions with oxygen, 7, 523 protonation, 7, 509 ring contractions, 7, 506 sigmatropic rearrangements, 7, 506 stability, 7, 492 N-substituted mass spectra, 7, 501 rearrangements, 7, 504 synthesis, 7, 536-537... 

Benzenediazonium fluoroborate, 2-carboxy-xanthone synthesis from, 3, 838 Benzenediazonium ions phenyl azide formation from, 5, 839 Benzenediazonium salts, o-(imidazol-l-yl)-intramolecular diazo coupling, 5, 404 Benzene-1,2-disulfonimides N-substituted reactions, 6, 930 Benzene episulfide formation, 7, 577 Benzeneimine... 

The original compound, maleimide (2,5-dioxo-A -pyrroline), is synthesized by the cyclo-condensation of ammonia and maleic acid. Similarly, primary amine is added to maleic anhydride, followed by cyclocondensation, to form N-substituted maleimide (Fig. 2). This reaction is applied to the preparation of bis-maleimides (BMl) [1]. At first, BMI was used as a crosslinking agent for natural rubber (NR). An o-dichlorobenzene solution of NR was crosslinked by BMI at I08-150°C in the presence of peroxides. The radicals generated from peroxides react with the double bonds of both BMI and NR [ 1 ]. 

A general method for malting Camps precursors has been developed/ Treatment of an anthranilic acid 15 with an acid anhydride or chloride in the usual way results in the corresponding benzoxazinone (16). Subsequent treatment with the dianion of an N-substituted acetamide furnishes P-keto amide 17. The reactions were run with crude 16, yields typically 50-80% overall. The effect of substituents on the reaction has not been extensively investigated. 

The Mannich reaction has been employed to obtain the pyr-N-substituted l,2,3,4-tetrahydro-j8-carboline 319, and intramolecular Mannich reactions at the pyr-N of suitably 1-substituted 1,2,3,4-tetrahydro-jS-carbohnes with formaldehyde 149,359-361... 

N-Substituted pyridinium salts are important synthetic reagents in many fields of organic chemistry, as evidenced by several comprehensive reviews that deal with their chemistry and reactions [53AG605 62AG811 63AG181 ... 

A great number of N-substituted 4-hydroxy-3-nitro-l,8-naphthyridin-2 (IH)-ones are obtained by reaction of N-substituted azaisatoic anhydrides with ethyl nitroacetate carbanion (Section II,A,4,a). A very specific method, more recently developed, is that of the inverse Diels-Alder method, involving the reactions of enamines with 5-nitropyrimidine (Section II,A,4,b). 

Alkylation of 737 with 738 gave 739 (81USP4252806). Reaction of 2-hydrazinoquinoline with the quaternary salts of N,N-substituted thioamides gave the hydrazones 735 whose cyclization in acetic acid gave triazoloquinolines 736 (80PJC661) (Scheme 127). 

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