Combined Furan C–H Activation and Furyl Ring-Opening by an Iron(II) Complex

Abstract

Cp*Fe[P(OCH2)3CEt]2Ph (Cp* = η5-1,2,3,4,5-pentamethylcyclopentadienyl, P(OCH2)3CEt = 2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane) reacts with furan and 2-methylfuran under photolytic conditions to selectively activate the α-C–H bond to produce Cp*Fe[P(OCH2)3CEt]2(2-furyl) and Cp*Fe[P(OCH2)3CEt]2[2-(5-methylfuryl)], respectively. Cp*Fe[P(OCH2)3CEt]2(2-furyl) reacts with internal alkynes (2-butyne, 3-hexyne, 1-phenyl-1-propyne) under photolytic conditions to produce sandwich complexes of the type Cp*Fe[η5-C5R4(CH═CHCHO)] (R = alkyl and/or aryl). Experimental data suggest a mechanism that involves phosphite dissociation and successive alkyne insertions into the Fe–furyl bond followed by furyl ring opening. Similarly, the methylfuryl analogue Cp*Fe[P(OCH2)3CEt]2[2-(5-methylfuryl)] reacts with 2-butyne to produce Cp*Fe[η5-C5Me4(CH═CHCOCH3)].