Imide halides

The observation that carboxyl ate ions react at a much faster rate than amines with nitrilium ions and that they give Z-O-acylisoamides only, has led to the development of a new method for the synthesis of peptides (13). Imide halide 4 on dissolution in a polar solvent undergoes rapid unimolecular ionization to the nitrilium ion 42 which reacts with the carboxylate ion to give the Z-O-acylisoamide 43 which in turn reacts with the amine to give the amide product 44. The formation of the amide (or peptide) can be carried out by adding the halide 41 to a solution containing both the amine and the carboxylic acid. The initial reaction (41 42 43) is best carried out at pH=6 and when the pH is adjusted to =8, formation of the amide (43 44)... 

A central theme of carbohydrate chemistry today is the construction of oligosaccharides as they are found in glycoproteins (H. Paulsen, 1990). Three closely related methods have proven to be reliable in complex syntheses, namely the halide, imidate, and thioglycoside methods. 

A method that achieves the same end result as that desired by alkylation of ammonia but which avoids the formation of secondary and tertiary amines as byproducts is the Gabriel synthesis Alkyl halides are converted to primary alkylamines without contam mation by secondary or tertiary amines The key reagent is the potassium salt of phthal imide prepared by the reaction... 

The cyclic sulfur imides readily undergo condensation reactions in the presence of a base, e.g., pyridine. For example, the reaction of S7NH with sulfur halides, S Cla or SOCI2, produces the series (S7N)2Sx (x = 1, 2, 3, 5), or (S7N)2S0, respectively. The bicyclic compound S11N2 (6.6) is obtained by treatment of 1,3-S6(NH)2 with The reaction... 

A variety of complexes of the thionyl imide anion [NSO] with both early and late transition-metal complexes have been prepared and structurally characterized. Since both ionic and covalent derivatives of this anion are readily prepared, e.g., K[NSO], McsMNSO (M = Si, Sn) or Hg(NSO)2, metathetical reactions of these reagents with transition-metal halide complexes represent the most general synthetic method for the preparation of these complexes (Eq. 7.10 and 7.11). ... 

In the presence of potassium carbonate, alkyl halides reacted with the imidic acid tautomers 154 of l,2,4-triazolo[l,5-c]pyrimidin-2-ones (153) to afford the 2-alkoxy derivatives 155 (85USP4528288 94JMC2371) (Scheme 60). 

Another alternative for preparing a primary amine from an alkyl halide is the Gabriel amine synthesis, which uses a phthalimide alkylation. An imide (—CONHCO—) is similar to a /3-keto ester in that the acidic N-H hydrogen is flanked by two carbonyl groups. Thus, imides are deprotonated by such bases as KOH, and the resultant anions are readily alkylated in a reaction similar to the acetoacetic ester synthesis (Section 22.7). Basic hydrolysis of the N-alkylated imide then yields a primary amine product. The imide hydrolysis step is analogous to the hydrolysis of an amide (Section 21.7). 

Rhenium(VI) complexes, 4,194 alkoxides, 4,196 amides, 4,194 amines, 4,199 carboxylates, 4,199 dimethylformamide, 4,199 dioxane, 4,198 halides, 4,195,199 2-hydroxypyridine, 4,199 imides, 4,194 magnetic behavior, 1,271 mixed sulfur-nitrogen compounds, 4,196 N heterocycles, 4,199 nitrides, 4,194 oxide halides, 4, 195 oxoanions,4,196 pyridine, 4,199 sulfates, 4,198 sulfur compounds, 4,196 tellurates, 4,198... 

Imides can be prepared by the attack of amides or their salts on acyl halides, anhydrides, and carboxylic acids or esters. The best synthetic method for the preparation of acyclic imides is the reaction between an amide and an anhydride at 100°C catalyzed by H2S04. When acyl chlorides are treated with amides in a2 l molar ratio at low temperatures in the presence of pyridine, the products are N,N-diacylamides, (RCO)3N. ... 

The imide nitrogen atom was also most reactive to a variety of electrophilic species (hydrogen halides, pseudohalogens, and alkyl halides) in the parent Rimidophosphazenes, R(C—NH)-N=PPh3. With t-butyl hypochlorite the /V-chloro-derivatives, R(C=NCl)-N=PPh3, were obtained. R/ -Vinyl-phenylphosphazenes have been prepared by condensation of aldehydes with active methylene compounds ... 

The synthetic potential of alkenylzirconium complexes is partially due to the fact that the hydrozirconation of alkynes can be carried out in the presence of some synthetically useful functional groups such as halide [80,153, 211, 212], acetals, amides, imides, carbamates, sulfides [186], ester, cyano [95, 213] and chiral propargyl amino functionalities [214]. 

Besides addition reactions, azides or hydrazoic acid can also yield tetrazoles through displacement reactions. Thus, halide displacement in imide chloride (78) yields 1,5-disubstituted tetrazoles (79), and in 2-chloro-pyridine (80), yields tetrazolopyridine (81) (Eq. 16a,b).141 143 Vinylogous... 

A simple two-step synthesis of 5H-alkyl-2-phenyloxazol-4-ones has been reported by Trost and coworkers (Scheme 6.209) [377]. a-Bromo acid halides were condensed with benzamide in the presence of pyridine base at 60 °C to form the corresponding imides. Microwave irradiation of the imide intermediates in N,N-dimethylacetamide (DMA) containing sodium fluoride at 180 °C for 10 min provided the desired 5H-alkyl-2-phenyloxazol-4-ones (oxalactims) in yields of 44—82%. This class of heterocycles served as excellent precursors for the asymmetric synthesis of a-hydroxycar-boxylic acid derivatives [377]. 

A plethora of weakly acidic pharmaceutical substances may be titrated effectively by making use of a suitable non-aqueous solvent with a sharp end-point. The wide spectrum of such organic compounds include anhydrides, acids, amino acids, acid halides, enols (viz., barbiturates), xanthines, sulphonamides, phenols, imides and lastly the organic salts of inorganic acids. 

---