Cycloaddition of nitrones with allenes. An example of steric control of regiochemistry

Padwa, Albert; Kline, D. N.; Koehler, Konrad F.; Matzinger, M.; Venkatramanan, M. K.

doi:10.1021/jo00226a035

Cited by 85 publications

(22 citation statements)

References 4 publications

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“…Scheme 2. 1,3-Dipolar cycloadditions between nitrones and the electron-deficient allenes 12 take place regioselectively to give the 5-methylene-isoxazolidines 13, which can be converted into the corresponding 4-isoxazolines 14 upon treatment with base or through thermolysis, by 1,3-hydrogen shifts (Scheme 3). [11][12][13][14][15] Scheme 3.…”

Section: 3-dipolar Cycloadditions Between Nitrones and Alkynes Or Amentioning

confidence: 99%

4‐Isoxazolines: Scaffolds for Organic Synthesis

Melo

2010

Eur J Org Chem

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Section: 3-dipolar Cycloadditions Between Nitrones and Alkynes Or Amentioning

confidence: 99%

4‐Isoxazolines: Scaffolds for Organic Synthesis

Melo

2010

Eur J Org Chem

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“…The thus formed initial products sometimes collapsed into secondary products via the N-O bond fission depending on the property of the substituent on the allenyl moiety and/or reaction conditions. [5][6][7][8][9][10][11][12][13][14][15] In contrast to the intermolecular reaction, there are very few examples of the intramolecular 1,3-diploar cycloaddition between the nitrone and allene groups. [16][17][18][19][20][21][22] Of particular interest among them is the reaction of the nitrone 1 16) derived from the reaction of 5,6-heptadien-2-one with Nmethylhydroxylamine (Chart 1).…”

mentioning

confidence: 99%

Regioselective Intramolecular [3+2] Annulation of Allene-Nitrones

Inagaki

Kobayashi

Mukai

2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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The regioselective intramolecular 1,3-dipolar cycloaddition of the phenylsulfonylallene-nitrone derivatives has been developed. This reaction showed that the distal double bond of the allene exclusively reacted with the nitrone group to produce the bicyclic isoxazolidine derivatives regardless of the substitution pattern on the allenyl moiety.Key words allene; nitrone; 1,3-dipolar cycloaddition Allene serves as a unique and powerful π-component in various types of cycloaddtions with an additional π-counterpart.1-4) It has been clarified that the intermolecular 1,3-dipolar cycloaddition of substituted-allenes with nitrones tends to undergo the regioselective ring closure to produce the corresponding methylene-substituted isoxazolidine derivatives. The thus formed initial products sometimes collapsed into secondary products via the N-O bond fission depending on the property of the substituent on the allenyl moiety and/or reaction conditions. [5][6][7][8][9][10][11][12][13][14][15] In contrast to the intermolecular reaction, there are very few examples of the intramolecular 1,3-diploar cycloaddition between the nitrone and allene groups. [16][17][18][19][20][21][22] Of particular interest among them is the reaction of the nitrone 1 16) derived from the reaction of 5,6-heptadien-2-one with Nmethylhydroxylamine (Chart 1). The in situ formed 1 (n=1) furnished the bicyclic isoxazolidine 2 in 45% yield via the cycloaddition with the distal double bond of the allenyl group, while the nonselective formation of the two bicyclic cycloadducts 3 (36%, two diastereoisomers in a ratio of 26 to 10) and 4 (29%) was observed when the one carbon-elongated nitrone 1 (n=2) was employed. The production of 3 could be rationalized in terms of the initial formation of compound 3′, which must have been derived by the participation of the proximal double bond of the allene. On the other hand, we have previously reported that the phenylsulfonylallene-azido derivative 5 was susceptible to the intramolecular 1,3-dipolar cycloaddition to exclusively produce the triazabicyclo[m.3.0]ring system 6 (m=3-5), 23) in which the distal double bond of the allene of 5 consistently took part in the ring-closing process unlike the case of compound 1 (n=2) (Chart 2). We describe here the highly regioselective intramolecular 1,3-dipolar cycloaddition of a series of phenylsulfonylallene-nitrone derivatives 7 with different substitution patterns on the allenyl moiety. Treatment of a 0.1 M solution of the aldehyde 8a 24) in EtOH with 3 eq of MeNHOH·HCl and NaHCO 3 at 0°C for 2 h effected the formation of the nitrone derivative 7a, followed by the 1,3-dipolar cycloaddition to give the 2-phenylsulfonyl-8-oxa-7-azabicyclo[4.3.0]non-1-ene (9a) in 54% yield (Table 1, entry 1). The ring closure exclusively occurred at the distal double bond of the allenyl moiety. This is in good accordance with the behavior of the phenylsulfonylallene-azido derivative 5 23) (Chart 2). A better yield (63%) was obtained when the reaction was performed at room temperature (entry 2). It ...

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“…This protocol delivers an intermediate cyano ketone through nucleophilic addition of the hydroxamate anion to 2,3-butadienenitrile and subsequent [3,3]-sigmatropic rearrangement and tautomerization. Formic Acid treatment of the cyano ketone then produces the 2-substituted indole.…”

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confidence: 99%

“…However, among cycloadditions involving 2,3-butadienenitrile, dipolar additions of nitrones are the most commonly encountered (eqs 10 and 11). 3 When the nitrone carries a sterically demanding group on the nitrogen, cis stereoselectivity is eroded (eq 11). A transformation reminiscent of eq 4 is illustrated in eq 12.…”

mentioning

confidence: 99%