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

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)].