名称:
C–S, C–H, and N–H bond cleavage of heterocycles by a zero-valent iron complex, Fe(N2)(depe)2 [depe=1,2-bis(diethylphosphino)ethane]
摘要:
Treatment of Fe(N-2)depe)(2) [depe = 1,2-bis(diethylphosphino)ethane] (1) with benzo[b]thiophene at room temperature results in the regioselective C-S and C-H bond cleavages giving Fe(SC6H4CH=CH)(depe)(2) (2a) and trans-FeH(C=CHC6H4S)(depe)(2) (3a) in 72 and 19% yields, respectively. Complex 1 also reacts with thiophene, 2- and 3-acetylthiophenes and 2- and 3-methylthiophenes to give both C-S and C-H bond oxidative addition products: Fe(SCH=CHCH=CH)(depe)(2) (2b) and trans-FeH(C=CHCH=CHS)(depe)(2) (3b), Fe[SC(COMe)=CHCH=CH](depe)(2) (2c) and trans-FeH[C=CHCH=C(COMe)S](depe)(2) (3c), Fe[SC(Me)=CHCH=CH](depe)(2) (2d) and trans-FeH[C=CHCH=C(Me)S](depe)(2) (3d), and Fe[SCH=C(Me)CH=CH](depe)(2) (2e) and trans-FeH[C=CHC(Me)=CHS](depe)(2) (3e), respectively. On the other hand, only C-H bond cleavage takes place in the reactions of 1 with furans such as furan, benzo[b]furan, and 2,3-dihydrofuran to give trans-FeH(C=CHCH=CHO)(depe)(2) (4a), FeH(C=CHC6H4O)(depe)(2) (4b) and trans-FeH(C=CHOCH2CH2)(depe)(2) (4c) and N-H bond is exclusively cleaved by the reaction of 1 with pyrroles such as pyrrole, indole and 2-acetylpyrrole to give trans-FeH(NCH=CHCH=CH)(depe)(2) (5a), trans- and cis-FeH(NCH=CHC6H4)(depe)(2) (5b) and FeH[NC(COMe)=CHCH=CH](eta(2)-depe)(eta(1)-depe) (6). Treatment of 2a with MeI results in the Fe-S bond cleavage of the thiaferracycle giving trans-FeI[(E)-CH=CHC6H4-2-SMe](depe)(2) (7) whose structure is unequivocally characterized by X-ray analysis. In contrast, hydrogenolysis of 2a with H-2 (50 atm) leads to the cleavage of the Fe-C bond of the thiaferracycle to yield cis- and trans-FeH(SC6H4-2-Et)(depe)(2) (8). (C) 1999 Elsevier Science S.A. All rights reserved.