Formation of substituted macrocyclic ethers by radical cyclisation

Beckwith, A. L. J.; Drok, Kitty; Maillard, B.; Degueil-Castaing, Marie; Philippon, Annie

doi:10.1039/a608494j

Cited by 18 publications

(16 citation statements)

References 14 publications

(8 reference statements)

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“…Remoção do gupo tert-butildimetilsilila com fluoreto de tetrabutilamônio 24,25 e subseqüente reação da hidroxila livre com brometo de alila 20 (31). Em seguida, redução quimiosseletiva do grupo azido a amino 23 e reação com cloreto de 2-iodobenzoíla 28 conduziriam à benzamida desejada (23), que seria então submetida à reação com hidreto de tri-n-butilestanho [29][30][31] .…”

Section: Resultsunclassified

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Dias¹,

Prado²,

Pinto³

et al. 2006

Quím. Nova

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Section: Resultsunclassified

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Dias¹,

Prado²,

Pinto³

et al. 2006

Quím. Nova

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“…Inicialmente, as reações de ciclização radicalar foram desenvolvidas utilizando-se as condições preconizadas para se minimizar a formação dos produtos de hidrogenólise e a ocorrência de reações intermoleculares, ou seja, alta diluição e adição lenta da solução de Bu 3 SnH e quantidade catalítica de AIBN em benzeno, sobre as soluções dos substratos (3 ou 4) em benzeno, sob refluxo 28,35,36 . Após eliminação do solvente, os resíduos obtidos foram submetidos à separação dos produtos em cromatografia em coluna de sílica.…”

Section: Resultsunclassified

Reações de carbociclização radicalar de orto-iodoaliloxibenzoatos derivados de d-glicose e d-galactose e comparação com as reações de seus análogos benzamidas

Binatti¹,

Alves²,

Filho³

et al. 2005

Quím. Nova

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“…These reaction conditions are recommended to improve the formation of cyclized products and to decrease the intermolecular reactions and the rate of hydrogen atom transfer to uncyclized radicals. [25][26][27][28] Two main products were formed in the radical reaction: the unexpected tetraorganotin(IV) compound 8 in 29% yield and the uncyclized reduced product 9 in 27% yield (Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

“…[22][23][24] The radical reaction was carried out using standard procedure. 1,2,25, To a solution of methyl 6-azido-2,3-di-O-benzyl-6-deoxy-α-D-galactopyranoside (0.40 g, 1.0 mmol) in CH 2 Cl 2 (8 mL) were added, under magnetic stirring, 50% (m/v) aqueous NaOH (3 mL) and Bu 4 NBr (0.48 g, 1.5 mmol), as phase transfer catalyst. The mixture was stirred for 15 minutes.…”

Section: General Proceduresmentioning

confidence: 99%

“…[25][26][27][28] When the addition of Bu 3 SnH/AIBN solution was made over a longer period (2.5 hours instead of 1 h) the yields of 8 and 9 reduced to 20% and 21%, respectively. When the concentration of Bu 3 SnH was reduced to 0.0065 mol L -1 and the addition of the reagents was maintained to 2.5 hours none of 8 was formed and the hydrogenolysis product 9 was obtained in 25% yield.…”

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confidence: 99%

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tri-n-butyltin hydride-mediated radical reaction of a 2-iodobenzamide: formation of an unexpected carbon-tin bond

Oliveira¹,

Prado²,

Alves³

et al. 2007

J. Braz. Chem. Soc.

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metila. A estrutura do produto foi elucidada por meio das espectrometrias de RMN unidimensionais ( 1 H, 13 C e DEPT) e bidimensionais (COSY e HMQC) e confirmada por espectrometria de massas. Foram apresentadas propostas de mecanismos para explicar a formação do derivado organoestanho.The tri-n-butyltin hydride-mediated reaction of methyl 2,3-di-O-benzyl-4-O-trans-cinnamyl-6-deoxy-6-(2-iodobenzoylamino)-α-D-galactopyranoside afforded an unexpected aryltributyltin compound. The structure of this new tetraorganotin(IV) product has been elucidated by 1 H, 13 C NMR spectroscopy, COSY and HMQC experiments and electrospray ionization mass spectrometry (ESI-MS). The formation of this new compound via a radical coupling reaction and a radical addition-elimination process is discussed. Keywords: tetraorganotin, arylstannane, aryl radical cyclization, 2-iodobenzamide IntroductionIn our studies of Bu 3 SnH-mediated radical cyclizations, we have applied unsaturated organohalides to synthesize large-and medium-size heterocycles. [1][2][3][4][5][6][7][8] Most particularly, ortho-iodobenzamides bearing a side allyloxy group have been used to form benzomacrolactams with 11-, 12-and 20-membered ring via regioselective endo aryl radical cyclization. [1][2][3][4][5] In this context, the benzamide methyl 4-Oallyl-2,3-di-O-benzyl-6-deoxy-6-(2-iodobenzoylamino)-α-D-galactopyranoside (1) was found to give the benzomacrolactam 2 owing to 11-endo cyclization in 32% yield. 2To continue these studies, we applied the Bu 3 SnHmediated radical reaction in an attempt to form the benzomacrolactams 3 and/or 4 from methyl 2,3-di-O-benzyl-4-O-trans-cinnamyl-6-deoxy-6-(2-iodobenzoylamino)-α-Dgalactopyranoside (5), a cinnamylated analogue of 1. Despite our knowledge of preferential endo cyclization mode over the exo-mode in macrocyclization reactions, 1-5,9-16 we expected that 10-exo cyclization could also occur due to the higher stability of the benzyl radical. This hypothesis was supported by the observation that precursors with cinnamyl group provided macrocycle intermediates resulting from 10-exo carbocyclization.6 Moreover, the cinnamyl moiety of 5 would generate a new stereogenic center upon 10-exo or 11-endo cyclization, hence the stereoselectivity of the reaction could be evaluated. In fact, the tri-n-butyltin hydridemediated reaction of 5 afforded an unexpected aryltributyltin compound. Results and DiscussionTo prepare the iodobenzamide 5, the C-4 and C-6 hydroxyl groups of methyl α-D-galactopyranoside were protected as benzylidene acetal 17 and the C-2 and C-3 hydroxyl groups were O-benzylated. 18 Removal of the benzylidene group 19 following by regioselective replacement of the hydroxyl group at C-6 by iodine atom, 2,20 substitution 365 Oliveira et al. Vol. 18, No. 2, 2007 of iodine atom by azido group 2,21 and O-cinnamylation of C-4 hydroxyl group 22 gave the methyl 6-azido-2,3-di-O-benzyl-4-O-trans-cinnamyl-6-deoxy-α-D-galactopyranoside (6). Selective reduction of the azido group 23 gave the expected amine 7, which upon treatment w...

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Formation of substituted macrocyclic ethers by radical cyclisation

Cited by 18 publications

References 14 publications

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Reações de carbociclização radicalar de orto-iodoaliloxibenzoatos derivados de d-glicose e d-galactose e comparação com as reações de seus análogos benzamidas

tri-n-butyltin hydride-mediated radical reaction of a 2-iodobenzamide: formation of an unexpected carbon-tin bond

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