Reaction with aqueous ammonia

An interesting divergence of behavior is observed with 2,3,5-trichloropyrazine, which on reaction with aqueous ammonia gives 2-amino-3,6-dichloropyrazine, whereas reaction with ammonia under pressure results in the formation of 2-amino-3,5-dichloropyrazine. 

In the following paragraph the nucleophilic substitution of some of the activated lactones under aqueous conditions will be discussed in detail, namely the reactions with aqueous ammonia, thereby yielding polyhydroxylated pyrrolidines (azafuranoses) and piperidines (azapyranoses). 

The dione 214 upon treatment with hydrazine afforded 215, which was converted into 2,2 -bis(bromomethyl)-3,3 -biquinazoline-4,4 -dione 217 (Scheme 47) via 216. The racemic 1,2,5-triazepine ( )-53 was obtained from 217 by reaction with aqueous ammonia in THF. The enantiomerically pure (—)-53 was formed by refluxing ( )-53 with (+)-CSA (camphorsulfonic acid) <1999CC1991>. It is interesting that this work is the first nonracemic example of a C2-symmetric bis-heterocycle, which is atropisomeric by virtue of retarded rotation around an N-N bond. 

When 2,5-diamino-l,3,4-thiadiazole is treated with an a-halo ketone in ethanol, the product is a 2-imino-3-(2-oxoalkyl)-5-amino-l,3,4-thiadiazoline hydrohalide (173). Direct treatment with excess hydrazine hydrate, or such treatment subsequent to reaction with aqueous ammonia, gives l-aminoimidazoline-2-thiones (Scheme 102) (70AHC(12)103). 

The crystalline 1,2,4-triazole derivative 236, on reaction with aqueous ammonia, gives l-/8-arabinofuranosylcytosine (237). Heating the more reactive 3-nitro-1,2,4-triazole derivative 238 with the weakly basic aniline in pyridine, followed by subsequent hydrolysis with aqueous ammonia. 

A -[(Methanesulfonyl)oxy]phthalimide undergoes a ring-expansion reaction with aqueous ammonia at room temperature to afford quinazoline-2,4(l//,3/f)-dione via a Lossen rearrangement. 2-Ureidobenzamide can be isolated as an intermediate when the reaction is performed under mild conditions and further cyclized to quinazoline-2,4(l//,3//)-dione by heating (cf. p 12). 

Acetone cyanohydrin, carbon disulfide and aqueous ammonia yield a product (D) with melting point 154—5° C while, with gaseous ammonia, together with (D) another product (E) with m.p. 297° C is formed. Christian (80) has repeated the reaction with aqueous ammonia, carbon disulfide and acetone cyanohydrin. He obtained a product with m.p. 153—4° C which he identified as 2,2,5,5-tetramethylimidazol-idine-4-thione (CLX, Ri=R2=Ra=R4=CH3 i.e. product D). It seems likely therefore that product (A) is 2,2,5,5-dipentamethyleneimidazol-idine-4-thione (CLX, Ri-l-R2=R3-(-R4= —(CHgjs—). 

Diethyl 2-hydroxy-3-(phenylamino)propylphosphonate is fonned by the reaction of diethyl 2,3-epoxypropylphosphonate with aniline at 120°C, and diethyl 2-hydroxy-3-aminopropylphosphonate is produced by the reaction with aqueous ammonia at room temperature. Ring opening at C-3 is also achieved with secondary amines such as piperidine in MeOH at 25-65°C, diethylamine at 100°C, or diethanolamine or 1,2,4-triazole in methyl ethyl ketone at 50°C in presence of a base (K2CO3, NaHCOj, CsF, or 1C X ). 

The pyrrolone (B) was obtained either from ethyl 4-bromo-3-methoxybut-2-enoate and sodium azide followed by subsequent reduction or directly by reaction with aqueous ammonia (Scheme 40). 

Tetrammineplatinum(II) chloride may be prepared by heating any one of the following with excess aqueous ammonia until a colorless solution results platinum(II) chloride tetrammineplatinum(II) tetrachloroplatinate(II) (Magnus s green salt), [Pt(NH3)4][PtCl4] diamminedi-chloroplatinum, [Pt(NH3)2Cl2] or a solution of tetra-chloroplatinic(II) acid. The present method involves the preparation of pure tetrammineplatinum(II) tetrachloro-platinate(II) and its subsequent reaction with aqueous ammonia. 

Production is carried out by liquid-phase synthesis from acetaldehyde and ammonia. Acetaldehyde is first trimerized to paraldehyde. The subsequent reaction with aqueous ammonia, which gives a 70% yield of 5-ethyl-2-methylpyridine, is performed in the liquid phase at 230 °C and at a pressure of around 150 bar with ammonium-salt catalysts. 

Yamane and Ren established an efficient molybdenum-mediated carbamoyla-tion of aryl halides [302, 303]. The procedure is simple and requires only a slight excess of carbon monoxide in the form of Mo(CO)g. This reaction provides a method for the synthesis of a variety of amides. Primary amides are also prepared in the reaction with aqueous ammonia (Scheme 2.48). Roberts and colleagues reported a similar reaction with microwave irradiation. 

PO also reacts with active hydroxyl hydrogen derived from the ring opening of other compounds such as EO and tetrahydrofuran thus, a copolymer polyol is obtained. Typically, polyols are obtained from base-catalyzed reactions with aqueous ammonia, sodium or potassium hydroxide, or lower alkyl tertiary amines such as trimethyl- and triethylamine. The reaction of PO with tetrahydrofuran is catalyzed by boron trifluoride etherate. The molecular weights of polyols prepared according to the reactions described earlier range from 200 to 7000. 

The intermediate sulfonyl chloride is converted to p-acetamidobenzene-sulfon-amide by a reaction with aqueous ammonia (Step 2). Excess ammonia neutralizes the hydrogen chloride produced. The only side reaction is the hydrolysis of the sulfonyl chloride to p-acetamidobenzenesulfonic acid. 

That a carbonamide rather than a thioamide is isolated in the Willgerodt reaction with aqueous ammonia does not constitute an argument against the above scheme, for hot aqueous ammonia is known to convert thioamides to carbonamides. The isomerization of straight-chain acetylenic compounds (with and without aromatic substituents) to products having the acetylene function in the terminal position is known to take place in the presence of sodium amide. The assumption that such unsaturated substances are intermediates in the Willgerodt reaction offers an explanation of the appearance of certain by-products. Tetra-hydronaphthoic acid, isolated in small amounts from the reaction of ethyl 6-tetralyl ketone with morpholine and sulfur, may arise from an oxidative attack by sulfur on an unsaturated intermediate. The presence of traces of thiophenes in the reaction mixtures is explicable when it... 

The synthesis of mPEG reagent 37 has been published in the patent literature as depicted in Equation 3.18. Tosylation of mPEG under standard conditions, followed by nucleophilic displacement reaction with aqueous ammonia solution gives mPEG-amine 42. Acylation... 

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