Halides, carbamoyl with

Resin-bound triazenes with a free NH group can be acylated by treatment with acyl halides, or carbamoylated by treatment with isocyanates [342]. The resulting triazene derivatives are stable towards strong bases, but undergo acidolysis when treated with TFA or TMSC1, yielding amides and ureas, respectively (Entries 1 and 2, Table 3.16). Polystyrene-bound triazenes devoid of a free NH group or carbamates can be cleaved from the support by treatment with acyl halides to yield amides (Entries 3 and 4, Table 3.16). 

Because many more alcohols than alkyl halides are commercially available, the Mitsu-nobu reaction enables the synthesis of larger and more diverse compound arrays than alkylation with alkyl halides. A -AcyIsuIfonamides are strongly acidic and can be alkylated with diazomethane (Entry 6, Table 8.9) or trimethylsilyldiazomethane [137]. Resin-bound sulfonamides have been N-acylated by treatment with acyl halides, and N-carbamoylated by treatment with isocyanates [138]. 

The most common reaction of selenolates is the nucleophilic substitution of halide compounds. For the synthesis of selenides 82 the selenolates 80 can be reacted with halides. Nucleophilic selenium species can also be reacted with a variety of other electrophilic compounds. The reaction with acid chlorides, chloroformates, or carbamoyl chlorides leads to the corresponding selenoesters 83 (R" = R ), selenocarbonates 83 (R" = OR ), or selenoamides 83 (R" = NR 2), respectively (Scheme 17).166... 

The lithium salts of acyclic secondary amines 92 can be conveniently transformed into the corresponding carbamoyllithiums 89 at —78 °C. Under these reaction conditions they react with trialkyltin chlorides to give carbamoyl stannanes 93 (Scheme 24)98. In the case of benzyl and allyl halides, an alkylation can occur affording products 94. However, when trialkylsilyl chlorides were used as electrophiles no carbamoyl silanes could be detected.. V-Alkyl thiocarbamates 95 can be prepared by reaction of the same intermediates 89 with sulfur followed by. S -alkylation at 0°C (Scheme 24)". 

Carbamoylation. The reagent does not react with benzaldehyde or ethyl benzoate. It reacts with alkyl iodides at 80°. A more useful reaction is that with acid halides, particularly acid bromides, which provides a useful route to a-kcto amides. The reagent does not react with cyclohexenone, but does react with methyl vinyl ketone in THF-HMPT (4 1) at -78° to give an adduct in 78% yield. 

The yields are lower because of competing hydrolysis during the aqueous work-up. Lithioynamines 44 must be used with unreactive halides such as carbamoyl chlorides and imidoyl halides (93) The scope of this reaction seems to be limited only by the availability of the requisite acyl chlorides. It is less surprising, therefore, that a single paper reports the preparation of about sixty push-pull acetylenes In contrast, silylated ynamines, react only with very strong acylation agents, e.g. trichloroacetyl and nitrobenzoyl chloride as well as with phosgeniminium chloride. 

The most important method for the preparation of aryl ketones is known as Friedel-Crafts acylation. The reaction is of wide scope. Reagents other than acyl halides can be used," including carboxylic acids," anhydrides, and ketenes. Oxalyl chloride has been used to give diaryl 1,2-diketones." Carboxylic esters usually give alkylation as the predominant product (see 11-11)." A-Carbamoyl p-lactams reacted with naphthalene in the presence of trifluoromethanesulfonic acid to give the keto-amide." ... 

A still unresolved problem is the structure of the often used adducts from phosphorus trihalides and carboxylic acid amides, which might be described by the formulae (8) or (9). With the aid of in situ generated adducts of acid amides and PX3 amidines, isonitriles, quinazolinones, alkyl chlorides, aminomethylenediphosphonic acids, carbamoyl halides, triformylaminomethane, 1,3,4-oxadia-zoles, sulfides (from sulfoxides), nitriles (from primary nitro compounds)" and bromoqui-nolines (from methoxyquinolines)" have been prepared. 

Direct carbamoylation of aryl halides with a carbamoylsilane can be performed under the action of catalysis by a Pd(0) complex (Scheme 10.230) [597]. The use of Pd(PPh3)4 is suitable for the conversion of unhindered aryl bromides and iodides into the corresponding amides. The carbamoylation of aryl chlorides and hindered aryl bromides, less reactive substrates, is effectively catalyzed by Pd(Pt-Bu3)2. 

Lewis acid-catalyzed condensation of an aryl carbonitrile (2 equivs.) with an acyl halide (1 equiv.) is a well-established and popular route to 1,3,5-oxadiazinium salts (see Section 6.18.10.3.l.i). The carbonitrile can be replaced successfully by aryl cyanates, cyanamides, and alkylthiocyanates, and examples using carbamoyl chlorides rather than the acyl halide have also been reported. The 1,3,5-oxadiazinium salts are also accessible by cyclocondensation of A-acylchloroformamidines with cyanamides in the presence of stannic chloride (see Section 6.18.10.2.2.l.i) and by condensation of A A -disubstituted-ALacylthioureas (2 equivs.) with thionyl chloride or phosphorus pentachloride (see Section 6.18.10.2.2.i). 

---