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

Tri-n-butyltin Hydride-Mediated radical reactions of ortho-and meta-Iodobenzamides to synthesize benzomacrolactams: surprising formation of biphenyl compounds from meta-regioisomers

“…5,13 In our previous papers we considered that the cyclization reactions were favoured by the conformational restriction present in the precursors due to the amide bond, the sugar moiety and the presence of a hydrogen bond formed between the hydrogen atom of the amide group and the oxygen atom of the allyloxy group. 6,7,9,35 The lack of cyclization products from radical reactions of 5 and 6 can indicate that the restricted rotation around the aryl-carbonyl bond present in 1 and 2 due to the iodine atom ortho to the amide group 36,37 also contributes to give a pre-organization to favour the ring closure. Despite this conformational restriction being absent in the aryl radicals, it is assumed that the relative amounts of Scheme 2.…”

“…In view of the numerous biological activities of macrolactams [1][2][3][4] and the synthetic challenge they present, 3,5 we have studied the Bu 3 SnH-mediated radical cyclization reactions using unsaturated iodides as precursors of macrolactams, [6][7][8][9][10][11][12] mainly allyloxy-ortho-iodobenzamides derived from carbohydrates to give benzomacrolactams. [6][7][8][9][10][11] These precursors furnished benzomacrolactams with 11-, 12-and 20-membered ring by regioselective endo aryl radical carbocyclization.…”

“…[6][7][8][9][10][11] These precursors furnished benzomacrolactams with 11-, 12-and 20-membered ring by regioselective endo aryl radical carbocyclization. [6][7][8][9] The benzamides methyl 4-Oallyl-2,3-di-O-benzyl-6-deoxy-6-(2-iodobenzoylamino)-α-D-galactopyranoside (1) and its gluco epimer 2 were found to furnish the benzomacrolactams 3 and 4 owing to 11-endo cyclization in 32% and 40% yield, respectively 6,7 ( Figure 1).Considering that (i) we have been stimulated to study the Bu 3 SnH-mediated radical reactions to construct Faraco et al 1505 Vol. 20, No.…”

“…20, No. 8, 2009 macrocycles, since there is a limited number of protocols available for the synthesis of large rings using free radical-mediated macrocyclizations, 13 (ii) the endomacrocyclization mode is favoured over the exo, [6][7][8][9]12,[14][15][16][17][18][19][20] (iii) the carbohydrate moiety impose conformational restriction to favour cyclization, [6][7][8][9]12 and (iv) although the majority of fused aromatic macrocycles have been obtained from ortho-halogenobenzene derivatives bearing an unsaturation in the side chain, [6][7][8][9][14][15][16][17][18][19] 3-halogenobenzene compounds have also been used as precursors of benzomacrolactams, 13 we selected to apply the Bu 3 SnHmediated radical reaction to the methyl 4-O-allyl-2,3- (Figure 2), the respective meta-isomers of 1 and 2 ( Figure 1), in an attempt to form the benzomacrolactams 7 and 8 ( Figure 2) by 12-endo carbocyclization. In view of the results of these radical reactions, we also carried out the Bu 3 SnH-mediated reaction with methyl 2,3-di-O-benzyl-6-deoxy-6-(3-iodobenzoylamino)-4-O-(1-pentenyl)-α-D-glucopyranoside (9) and methyl 2,3-di-O-benzyl-6-deoxy-6-(2-iodobenzoylamino)-4-O-(1-pentenyl)-α-Dglucopyranoside (10) to synthesize the respectively 14-and 13-membered lactams 11 and 12 (Figure 2).…”

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

“…[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. 2 To 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.…”