Amino-migration reaction

Recently, Kawase developed a new synthesis for dibenzopentalene from an indenone derivative prepared by a novel amino-migration reaction. The reaction of 2,2 -dilithiotolan, generated from corresponding dibromide 284, with Af,Af-dimethylbenzamide produces 2-(2-benzoylphenyl)-3-phenylindenone 285 in 65% yield, the structure of which was determined by crystallographic analysis. The McMurry reaction of 287 subsequently leads to dibenzopentalene 256 in 58% yield (Scheme 6.71) [166]. 

Crossover experiments have been used to establish that the novel N to C acyl migration reaction of acyclic imides (69), to give o -amino ketones (70), proceeds by intramolecular reaction of the base-generated carbanion. ... 

Hara, O. Ito, M. Hamada, Y. Novel N-C acyl migration reaction of acyclic imides a facile method for a-amino ketones and / -amino alcohols. Tetrahedron Lett. 1998, 39, 5537—... 

Acylation. Reaction conditions employed to acylate an aminophenol (using acetic anhydride in alkaU or pyridine, acetyl chloride and pyridine in toluene, or ketene in ethanol) usually lead to involvement of the amino function. If an excess of reagent is used, however, especially with 2-aminophenol, 0,A/-diacylated products are formed. Aminophenol carboxylates (0-acylated aminophenols) normally are prepared by the reduction of the corresponding nitrophenyl carboxylates, which is of particular importance with the 4-aminophenol derivatives. A migration of the acyl group from the O to the N position is known to occur for some 2- and 4-aminophenol acylated products. Whereas ethyl 4-aminophenyl carbonate is relatively stable in dilute acid, the 2-derivative has been shown to rearrange slowly to give ethyl 2-hydroxyphenyl carbamate [35580-89-3] (26). 

The reaction of 3-amino-1,2,4-triazine 1-oxide 1 with methyl iodide in the presence of sodium bicarbonate leads to the methylation of the amino group to afford 3-methylamino-l,2,4-tiiazine 1-oxide 123. This iV-oxide 123, under neutral conditions in the presence of Mel, undergoes methyl group migration to the N(2) atom of the 1,2,4-triazine ring, yielding 3-imino-2-methyl-1,2,4-triazine 1-oxide 124. The same product 124 was obtained by direct methylation of compound 1 under neutral conditions (84TL1677). 

Reaction of the glycol, 70, affords an oxazolidinone rather than the expected carbamate (71) on fusion with urea. It has been postulated that the urea is in fact the first product formed. This compound then undergoes 0 to N migration with loss of carbon dioxide reaction of the amino alcohol with the isocyanic acid known to result from thermal decomposition of urea affords the observed product, mephenoxolone (74) this compound shows activity quite similar to that of the carbamate. An analogous reaction on the glyceryl ether, 75, affords metaxa-lone (76). 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

Deamination reactions of (2-amino-l,l-dimethyl)ethyldiphenylphosphine oxide (57) result in the formation of three products, in each of which the diphenylphosphinyl group has migrated to the primary carbon of the starting material. These reactions are unusual examples of non-assisted migration of a phosphinyl group. 

This is clearly demonstrated in the pinacolinic deamination (cf. p. 114) of an optically active form of the amino-alcohol (50). Such reactions proceed from a conformation (antiperiplanar 50a or 50b) in which the migrating (Ph) and leaving (NH2 as N2 cf. p. 114) groups are TRANS to each other. Rearrangement via a bridged carbocation would necessarily lead to 100% inversion at the migration terminus in the product ketone (5lab), whichever initial conformation, (50a) or (50b), was involved ... 

A similar reaction of a silicon-amino substituted silene [11] supports this mechanism. The migration of a trimethylsilyl group from the Si-amino substituent to the nucleophilic carbon atom of the Si=C moiety leads to the diazasilacyclopentane 30. 

Since the migration of a C=C bond to form a C=N bond is impossible, the corresponding reaction with diethylamine afforded 2-amino-2-alkenyl phosphonates (Scheme 10.75) [83a]. 

The reaction of diethylamine or alcohol with 2,3-allenamide 551 affords /3-diethyl-amino-a,/3-unsaturated enamide 555, indicating the migration of the C=C bond under basic conditions. The corresponding reaction of 551 with benzyl thiol proceeded to afford /j-thiobenzy 1-/1,y-unsatu rated enamide 556 the /i,y-C=C bond can migrate to the a,/3-position on the treatment with DBU in THF to afford 557 [257]. In reactions of 4,4-dichloro-2,3-butenamide 558 with amines, thiolates and alcohols, ce,/j-unsaturated enamides 560-564 are always formed on treatment with a base [258, 259]. 

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