Acylaminal

The N-oxides of isoquinolines have proved to be excellent intermediates for the preparation of many compounds. Trialkylboranes give 1-alkyl derivatives (147). With cyanogen bromide in ethanol, ethyl N-(l- and 4-isoquinolyl)carbamates are formed (148). A compHcated but potentially important reaction is the formation of 1-acetonyLisoquinoline and 1-cyanoisoquinoline [1198-30-7] when isoquinoline N-oxide reacts with metbacrylonitrile in the presence of hydroquinone (149). Isoquinoline N-oxide undergoes direct acylamination with /V-benzoylanilinoisoquinoline salts to form 1-/V-benzoylanilinoisoquinoline [53112-20-4] in 55% yield (150). A similar reaction of AJ-sulfinyl- -toluenesulfonamide leads to l-(tos5larriino)isoquinoline [25770-51-8] which is readily hydrolyzed to 1-aminoisoquinoline (151). 

Smooth acylaminations are also given by isocyanate adducts of 3-phenyloxaziridine. Ammonia and primary as well as secondary amines form the corresponding semicarbazides, e.g. (102). Owing to the fast amination reaction, shortlived substances like triazanes become accessible, e.g. the cyclohexyl compound (103), which is stable for only a few minutes at room temperature. 

It has been found that the fusion of the pyrazole with the pyrrole ring is difficult, probably for steric reasons. All attempts to cyclize 3-amino- and 5-amino-4-acetylenylpyrazole have failed. For example, upon prolonged heating of 5-amino-4-acetylenylpyrazole 68 in DMF in the presence of Cul and (or) CuC=CPh, side transformations andresinification occurred. The side processes were suppressed by acylation of the amino group and substitution of DMF by inert cyclohexane. However, 80-90% of the starting compounds was recovered after heating acylamine... 

The next step in the development of periodate oxidation was made by Nicolet and Shinn.8 They applied periodate oxidation to a series of a-amino acids, and found that those containing the 2-hydroxyamine structure are almost instantaneously oxidized. For such an oxidation to proceed rapidly, the amine could not be tertiary. An a-hydroxy A-acylamine was attacked very slowly, if at all. Only a small number of compounds were investigated. 

Trimethylsilylketene reacts smoothly with u./V-diarylnitrones to give oxoin-doles in good yields. On the other hand, the reaction of trimethylsilylketene with N-arylmethylnitrones gives a mixture of N,N-diacylamines and N-acylamines (Scheme 2.315) (836). 

The INAS reaction of to-vinyl amides proceeds as shown in Eq. 9.42 to afford cyclopropylamine derivatives [77]. The reaction with cyclic imides derived from ovinylamines, furnishing acylaminal derivatives, was also found to proceed smoothly (Eq. 9.43) [78]. 

A related approach consists in the generation of endocyclic iminium ions from fV-acylaminals 209. As in the previous case, their treatment with boron trifluoride induces a diastereoselective cyclization, and thiazolo[3,4- ]pyridines 210 are isolated in good yields (Scheme 59) <2001EJ01267>. Alkenes can also participate and react well with the intermediate... 

In cases of some derivatives bearing an amino substituent, conversions to acylamines, alkylamines, and amidines have been reported. These substrate amines include the above-mentioned two amino compounds 157 and 159 as well as other compounds shown in Scheme 25. 

The reactions of tetra-O-acylgluco- and -galactopyranosylaminomethy-lenemalonates (1444) and bromine in a mixture of chloroform and water at room temperature for 2 days gave the corresponding tetra-O-acylamine hydrobromides (1445) in 81-96% yields (86MI8). 

In contrast to the results obtained by Jacobsen et al. when utilizing Schiff base catalyst 42, the decrease of reaction temperature to -40 °C reduced the yield as well as enantioselectivity of the resulting Mannich adduct (Scheme 6.175) [201]. Catalyst 198 found to be less effective in the Mannich reaction in terms of yield and enantiomeric induction due to reduced basicity of the N-acylamine and weaker hydrogen-bonding interactions compared to the more basic Strecker substrates (Scheme 6.174). 

In studying the reactions betw nitroso-acylamines and diazo esters several expl compds were prepd. Some reactions involved explosion hazards) 4) F. Bucci, AnnChim (Rome), 41, 587-93(1951) CA 47, 3443 (1953) (Reactions of alkali nitrites with some otg amines, such as urea may result in explns) 5) G. Armistead, ChemEngt-Progress 48, 5-10(1952) CA 46, 2298 (1952) (A review of expln hazards)... 

Resin-bound diols, amino alcohols, and dithiols, which reversibly form cyclic acetals with aldehydes and ketones, have been successfully used as linkers for carbonyl compounds (Entries 5-11, Table 3.40). Acetal formation on insoluble supports can be achieved by azeotropic removal of water (C6H6, TsOH, reflux [720]), whereas dithio-acetals can be prepared by acid-catalysis alone (BF3 OEt2 or TMSC1 CHCI3,0 °C, 2 h [721]). /V-Acylaminals such as R-CFI(OMe)NFI-CO-Pol have been prepared by treatment of resin-bound amides H2NCO-Pol with aldehydes in the presence of HC(OMe)3 and TFA [722],... 

Support-bound C,F I-acidic compounds, such as acetoacetamides, react with isocyanates under basic conditions to yield amides through C-carbamoylation [71]. Similarly, polystyrene-bound aryllithium compounds can be converted into benzamides by treatment with isocyanates [111]. These reactions are closely related to C-thiocarbamoyla-tion, which has been used for the solid-phase synthesis of thioamides (see Section 13.9). Amides have also been prepared by C-alkylation of resin-bound N-acylaminals with allyltrimethylsilane or diethylzinc (Entry 11, Table 13.7). 

It has been known for a long time 82> that N-nitroso-acylamines rearrange to azo compounds ... 

Treatment of an w-acylaminal derivative 83 with allylsilanes in the presence of a Lewis acid or a Brpnsted acid gives the corresponding condensation products (equation 55)122-125. The reaction can also proceed intramolecularly, e.g. in the formation of 84 and 85 (equations 56 and 57). A piperidine skeleton 86 can also be formed by such intramolecular cyclization (equation 58)126. 

The /V-acylaminals 136 can serve as substrates for the formation of fused azepinone derivatives on treatment with a catalytic amount of TiCh, although the reaction is sensitive to the nature of the R group. Thus, 138 was obtained from 136 (R = CH2OAc), but with R = Me in 136, the 6,6-fused system 137 resulted (Scheme 18) <1999TL7939>. 

Stable aryl- and alkyl-substituted disilenes undergo the [2 + 4] cycloadditions with benzyl, acylamines, and 1,4-diazabutadienes but not with 1,3-butadienes.77 131 On the other hand, stable tetrasilyldisilene 22 reacts with 2,3-dimethyl-1,3-butadiene at rt giving the corresponding 4,5-disilacyclohexene 218 [Eq. (104)].127 The reason for... 

The synthesis of alkaloids described above is based on the generation of a cationic center at the position a to the nitrogen atom of an amide followed by a carbon-carbon bond formation at the a-position as the key reaction. On the other hand, developing an anionic center at the a-position of the N-acylamine generally requires a very strong base which may bring about undesirable side reactions. However, the formation of... 

Meth-Cohn and Suschitzky41 examined this reaction further and observed that the acylamines (131) reacted as easily and more cleanly than the parent amines, especially with performic acid (see... 

Acylamino cyclization.l0 The indolizidine alkaloid (- )-swainsonine (3) has been synthesized by radical cyclization of the acylamine 1, derived from D-tartaric acid, to provide the indolizidinones 2 in 71% yield. Conversion to the alkaloid (3) included removal of the keto group by conversion to the thiolactam by Lawesson s reagent (97%) followed by desulfurization with Raney nickel (96% yield). 

E)-acylamine (285), which in the Diels-Alder reaction must have a transition state where the W-acyl group is endo and the ester group is exo in order to account for the formation of the trans product (286) (80JA1153). 

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