The structure of benzyl N-(tert-butoxycarbonyl)oxamate, C14H17NO5

Wyss, Heinz; Brisse, F.; Hanessian, Stephen

doi:10.1107/s0108270184009975

Cited by 4 publications

(3 citation statements)

References 6 publications

(6 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The bond length between the two sp 2 -hybridized carbon atoms C19 and C21, 1.522(3) Å, indicates that there is practically no conjugation between the π-electron systems of the amide and ester groups. In benzyl N -( tert -butoxycarbonyl)oxamate, where these two groups were twisted by 90°, the analoguous bond was only slightly elongated [1.533(2) Å]. The ethyl group is in a staggered conformation with respect to the carboxy group.…”

Section: Resultsmentioning

confidence: 99%

Reactions of N-Aryl-N-(4,5-dihydro-1H-imidazol-2-yl)hydroxylamines with Electron-Deficient Acetylenes. Synthesis and Structure of Novel Heterocyclic Ketene Aminals

et al. 1996

View full text Add to dashboard Cite

Reactions of the title hydroxylamine hydrochlorides 1 with electron-deficient acetylenes 3 are described. Compounds 1a reacts with ethyl propiolate (3a) to give the expected indole 7. Similar reactions of 1a-e with disubstituted acetylene derivatives such as diethyl acetylenedicarboxylate (3b), dimethyl acetylenedicarboxylate (3c), or ethyl phenylpropiolate (3d) lead to the formation of novel heterocyclic ketene aminals 9a-m. X-ray crystal structure and NMR spectra of 9a are described in detail. hydroxylamine hydrochlorides 1 are readily prepared by reacting 2-chloro-4,5-dihydroimidazole with suitable N-aryl-hydroxylamines 1,2 and could be converted to the free bases 2 on treatment with methanolic NaOH. 3 Our detailed studies on the structure of 2 revealed that in the crystalline phase the compound 2a (R ) H) exists as a 1:1 mixture of two tautomeric forms: A (R-iminohydroxylamine) and B (R-aminonitrone). On the other hand, NMR spectra suggested that in solution the nitrone form B prevails 3 (Scheme 1). NThe reactions of various N-arylnitrones or N-arylhydroxylamine derivatives with acetylenes bearing electronwithdrawing groups have been studied in a number of laboratories. Thus, it has been reported that the reaction of R-aryl-N-phenylnitrone with hexafluoro-2-butyne leads to 2,3-bis(trifluoromethyl)indole 4 and the treatment of N-arylhydroxylamines or hydroxamic acids with activated monosubstituted acetylenes gives rise to the formation of indoles functionalized at the C-3 carbon via tandem Michael addition-[3,3]sigmatropic rearrangement reaction. 5,6 As an extension of our study on the reactivity of hydroxylamines 1, 1 this paper deals with the reactions of the hydrochlorides 1 or corresponding free bases 2 with a variety of electron-deficient acetylene derivatives 3. Results and DiscussionFirst, the hydrochloride 1a was subjected to the reaction with ethyl propiolate 3a in the presence of a 2-fold excess of Et 3 N, and the expected indole 7 was obtained in 65% yield (Scheme 2). To examine what effect acetylene substituents would have on the reaction course, we attempted a similar reaction of 1a with diethyl acetylenedicarboxylate 3b. The only product that could be isolated in pure form (31% yield) from the complex mixture of products was the ketene aminal 9a (Scheme 2). When the free base 2 was used instead of salt 1a, the compound 9a was obtained in 22% yield only, and therefore, the hydrochlorides 1a-d were found to be more suitable substrates for preparation of a series of novel ketene aminals 9a-m. In general, the reactions of 1 with activated acetylenes were performed in polar aprotic solvents such as THF or acetone at room temperature and gave the desired products in 10-39% yields.Plausible routes to the formation of 7 or 9 are shown in Scheme 2. We assume that the mechanism of the reaction leading to the indole 7 is analogous to those previously described 2,3 and consists of loss of a water molecule from the intermediate 6. Alternatively, 6 can undergo a retro-ene reaction leading to reopening of the...

show abstract

Section: Resultsmentioning

confidence: 99%

Reactions of N-Aryl-N-(4,5-dihydro-1H-imidazol-2-yl)hydroxylamines with Electron-Deficient Acetylenes. Synthesis and Structure of Novel Heterocyclic Ketene Aminals

et al. 1996

View full text Add to dashboard Cite

show abstract

“…This finding conforms to the previous observation that this bond is cleaved by aminolysis and the reaction conditions are mild in comparison with other amides without the tert-butoxycarbonyl group (Boc). However, the carbamate bond lengths C2--N1 are also longer 178-1 (3) 59"2 (7) 6'2 (7) -r' = ~o~ + oJ2 0"0(4) Xc = o~ -o~3 + 180 -0'2(4) -6"0 (7) (mod 360) than usual although several similar cases have already been encountered (Wyss, Brisse & Hanessian, 1984;Albright & Moran, 1986;Cambridge Structural Database, 1988). In Boc-alanine and Boc-proline these bond lengths were found to be 1.344 (5) and 1.346 (4)/~, respectively (Benedetti, di Blasio, Pavone, Pedone, Toniolo & Bonora, 1981;Benedetti, Ciajolo & Maisto, 1974).…”

Section: (5)mentioning

confidence: 99%

Structures of tert-butyl N-benzoyl-N-phenylcarbamate and tert-butyl N-acetyl-N-phenylcarbamate

Symerský¹,

Maloň²,

Grehn³

et al. 1990

Acta Crystallogr C

View full text Add to dashboard Cite

show abstract

“…Only one similar compound, (II) (Wyss & Brisse, 1984), has been found in the Cambridge Structural Database (CSD, Version 5.24 of April 2003;Allen, 2002) which differs from (I) in the terminal groups: the benzyl group in (I) is replaced by a tert-butyl group in (II) and the methyl group in (I) is replaced by a benzyl group in (II). Although this leads to a completely different conformation of (II), the latter also packs as hydrogen-bonded dimers.…”

mentioning

confidence: 99%

MethylN-(benzyloxycarbonyl)oxamate

2003

View full text Add to dashboard Cite

The title compound, C 11 H 11 NO 5 , is almost planar. The molecules pack as hydrogen-bonded dimers. Comment N-and C-protected ethyl oxamates are excellent nitrogen nucleophiles in Gabriel reactions (Berre Â e et al., 1999). They are available by oxidation of protected serine or threonine (Stachulski, 1982). For our synthesis of methyl N-(benzyloxycarbonyl)oxamate, (I), we chose oxidation with RuO 2 / NaIO 4 (Garner & Park, 1990), which leads to better yields.

show abstract

The structure of benzyl N-(tert-butoxycarbonyl)oxamate, C14H17NO5

Cited by 4 publications

References 6 publications

Reactions of N-Aryl-N-(4,5-dihydro-1H-imidazol-2-yl)hydroxylamines with Electron-Deficient Acetylenes. Synthesis and Structure of Novel Heterocyclic Ketene Aminals

Reactions of N-Aryl-N-(4,5-dihydro-1H-imidazol-2-yl)hydroxylamines with Electron-Deficient Acetylenes. Synthesis and Structure of Novel Heterocyclic Ketene Aminals

Structures of tert-butyl N-benzoyl-N-phenylcarbamate and tert-butyl N-acetyl-N-phenylcarbamate

MethylN-(benzyloxycarbonyl)oxamate

Contact Info

Product

Resources

About