Acetic anhydride—Triethylamine

Hydroxvthiazolium hydroxide inner salts (2) (X = 0) have been synthesized by an improved acetic-anhydride-triethylamine-caialyzed cyclization of N-substituied N-thiobenzovlalanines (Scheme 15) (23). 

The elaboration of 113 to (—)-kinamycins C, F, and J, is shown in Scheme 3.19. To access ( )-kinamycin C (3), the silyl ether function of 113 was cleaved with aqueous hydrochloric acid (95 %). Alternatively, treatment of 113 with lithium hydroxide served to liberate the phenol function and saponify the three acetate esters, to provide ( )-kinamycin F (6) in 92 % yield. Finally, acylation of the tertiary hydroxyl of 113 (acetic anhydride, triethylamine) afforded a tetraacetate. Cleavage of the silyl ether then provided ( )-kinamycin J (10) in 80 % over two steps. 

Ph, R = H) and acetic anhydride-triethylamine was initially thought to be anhydro-2,3-diphenyl-4-hydroxy-l,3-thiazolium hydroxide, CijHiiNOS (114, R = R = Ph, R = H), but later studies established that the product had the molecular formula C30H24N2O2 and the constitution 116. The synthesis of the meso-ionic l,3-thiazol-4-one (114, R = R = Ph, R = H), orange-yellow needles, m.p. 113°-115°, was successfully achieved by dehydration of the acid (115, R = R = Ph, R = H) using acetic anhydride-triethylamine for a few minutes at room temperature. The acids (115, R = NR2, R = Ph, R = H) and acid anhydrides similarly yield the corresponding meso-ionic l,3-thiazol-4-ones (114, R = NRj, R = Ph, R = H). Analogous polycylic meso-ionic l,3-thiazol-4-ones have also been prepared. ... 

The dehydration of thiobenzoylthioglycolic acid (135, R = Ph, R = H) with acetic anhydride-boron trifluoride was initially described as yielding the meso-ionic l,3-dithiol-4-one (134, R = Ph, R = H), but subsequent studies showed that the product was in fact the 5-substituted derivative 134, R = Ph, R = COCHjSCSPh. Authentic meso-ionic l,3-dithiol-4-ones (134) have recently been prepared (85-90% yield) by the cyclodehydration of the acids (135) with acetic anhydride-triethylamine at 0°-10°. Examples include anhydro-4-hydroxy-2-phenyl-l,3-dithiolium hydroxide (134, R = Ph, R = H) described as scarlet needles, m.p. 113°—115° this compound is sensitive to moisture. Anhydro-4-hydroxy-2,5-diphenyl-1,3-dithiolium hydroxide (134, R = R = Ph) was obtained as gold lustered, deep violet needles,... 

The a-selenoacid (506) with acetic anhydride-triethylamine at room temperature gave the meso-ionic l,3-selenazol-4-one (505, R = R = R = Ph) as magenta needles in 80% yield. This new meso-ionic... 

One of the original routes into [18]annulenes (e.g. 44) possessing heterocyclic rings utilized the Perkin condensation (acetic anhydride-triethylamine). This cyclocondensation procedure transformed (45) and (46) into (44) in low yield the overall results have been reviewed (77CRV513). 

Nickel Raney Sodium hydroxide Sodium carbonate Potassium phthalimide 4-(m-Chlorophenyl)-l-piperazinopropionitrile Acetic anhydride Triethylamine... 

It has been shown (76JOC1724) that a previously described compound (65BCJ596), prepared by treatment of thiobenzoylthioglycollic acid (264) with acetic anhydride in the presence of boron trifluoride, is indeed the acylated 1,3-dithiolone (265) and not the claimed 2-phenyl-l,3-dithiolylium-4-olate. The latter can be prepared from thiobenzoylthioglycollic acid (264) and acetic anhydride-triethylamine (76JOC1724) or acetic anhydride-dicyclohexyl-ethylamine (76CB740). 

Acetamido-6-deoxy-D-fructose exists as a furanose form, and gives with methanolic hydrogen chloride an anomeric mixture of the furano-sides. 6-Acetamido-6-deoxy-L-xf//o-hexulose was obtained as a syrup which showed a distinct Amide II band. Regardless of whether the free 6-acetamido-6-deoxy-L-xi/Zo-hexulose was prepared by hydrolysis of 6-acetamido-6-deoxy-2,3-0-isopropylidene-a-L-3C[/Io-hexulofuranose or by N-acetylation of 6-amino-6-deoxy-L-xyZo-hexulo-furanose hydrochloride with acetic anhydride—triethylamine in aqueous methanol, there appeared in both cases only the furanose form of the L-xj/Zo-hexulose derivative. ... 

The precursor to amidoacrolein 64, 1,3-dioxin 66, was prepared as follows [39] the imine derived from the condensation of 2,2-dimethyl-l,3-dioxan-5-one with aminoacetaldehyde dimethyl acetal was acetylated with acetic anhydride/triethylamine to afford dioxin 66 in 83% yield (Scheme 24). Retro Diels-Alder of dioxin 66 in warm benzonitrile (120 C, 16 h) generated the amidoacrolein 64, which was trapped in situ with the silyloxydiene 65 to afford the desired cycloadduct 63 (64%). An aldol cyclization between the acetamide and neighboring aldehyde functionalities within 63 proceeded smoothly (2 equiv. of KCh-Bu, 10 equiv. of EtOAc, THF, 0 °C, 40 min) and directly afforded the corresponding conjugated lactam. This product was of sufficient purity for the second aldol reaction, which was best accomplished under acidic conditions, presumably proceeding through the achiral keto aldehyde intermediate 62 enroute to the desired, but racemic, (3-hydroxy ketone 61 obtained in 79% yield after the two consecutive ring closures. 

Category Ilae cyclizations play a prominent role in the synthesis of isoindoles. Simple 2-alkyl-2/f-isoindoles can be prepared from l,2-bis-(bromomethyl)benzene via dihydroisoindole-A(-oxides. The oxides undergo Polonovsky elimination in acetic anhydride/triethylamine <88CZ85>. A similar reaction sequence can be applied to the synthesis of 2-aryl analogs (Scheme 72) <87CZI55>. 

A mixture of 338.5 g acetic anhydride (3.3 mol), 45 g acetic acid (0.75 mol), 379.5 g triethylamine (3.75 mol), and 1.83 g 4-(dimethylamino)-pyridine (0.015 mol) in a reaction vessel was heated to 50°C. Then 135 g racemic alanine (1.5 mol) was added as a solid over 6 h thereby maintaining the reaction temperature at 45-55°C. After completion of the alanine addition, the reaction mixture was stirred at 50°C for an additional 8 h. Acetic anhydride, triethylamine, and acetic acid were distilled off by vacuum distillation (10-15 mbar), while gradually raising the jacket temperature to a maximum of 100°C. The residue (GC assay >95% acylaminoketone intermediate) was cooled to room temperature and diluted with 815 mL water. Malonodinitrile (94.5 g, 1.425 mol) was added, and this mixture was slowly added to 500 g aqueous sodium hydroxide solution (30%). The speed of addition was adjusted so that the reaction temperature did not exceed 60°C. The resulting suspension was cooled to 0°C, filtered, washed with water, and dried in vacuum at 55°C to yield 168 g 2-amino-3-cyano-4,5-dimethylpyrrole, in a yield of 83% for the total of the two steps, m.p. (DSC) 172°C. 

The N-oxides of N-substituted isoindoHnes 5 (easily accessible from o-xylylene dibromide (4)) are dehydrated by acetic anhydride/triethylamine to give N-substituted isoindoles 6 [210] ... 

Preparative Methods (i) from 3-trimethylsilyl-2-propyn-l-ol by reduction (sodium bis(2-methoxyethoxy) aluminum hydride (Red-Al), 70%) and acetylation (acetyl chloride, pyridine, 78%) (ii) from 3-trimethylsilyl-2-propyn-l-ol by reduction (P-2 raney nickel, H2, 86%) and acetylation (iii) from ally-loxytrimethylsilane by a metalation-rearrangement sequence (f-butyllithium, 90%) and acetylation (acetic anhydride, triethylamine, 76%). ... 

On the other hand, acetic anhydride/triethylamine or acetyl chloride/triethyl-amine or TFAA/triethylamine gave symmetrical maleimide. 

Acetic anhydride-triethylamine Isoindoles from isoindoline N-oxides s. 20, 648a suppl. 29... 

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