Abstract
The reactivity of (1-hetero-1,3-diene)tricarbonyliron(0) complexes has been investigated with particular emphasis being placed on their reactions with lithium amides and hydride transfer reducing agents. Reaction of (1-hetero-1,3-diene)tricarbonyliron(0) complexes with both primary and secondary lithium amides gives different products depending upon the nature of the heteroatom and the substituent at position 2. Reaction of lithium amides with (PhCH=CHC(R1)=NR2)Fe(CO)3 (R1=CH3, R2=Ph, PhCH2, p-C6H4OCH3, CH(CH3)2)] leads to formation of novel complexes [(PhCH=CHC(NHR2)=CH2)Fe(CO)3 (R2=Ph, PhCH2, p-C6H4OCH3, CH(CH3)2)]. Reaction of lithium amides with (PhCH=CHC(R1)NR2)Fe(CO)3 (R1=H, R2=Ph) results in attack at a coordinated carbonyl ligand leading to formation of formamides. Previous work concerning the hydride reduction of (1,3-diene)tricarbonyliron(0) complexes has been extended to larger molecules of biological interest. Reduction of (ergosteryl acetate)tricarbonyliron(0) with lithium aluminiumhydride affords 5alpha-ergosta-7,22-dien-3beta-ol while reduction of (16-dehydropregnenylone acetate)tricarbonyliron(0) leads to a mixture of products. In both cases deuterated analogues were synthesised in order to obtain mechanistic information. Reaction of (PhCH=CHO(R)=O)Fe(CO)3 (R=H, CH3, tBu) and (PhCH=CHO(R1)=NR2)Fe(CO)3 (R1=H, CH3, R2-Ph, p-C6H4OCH3) with DIBAL, LiEt3BH and LisBu3BH leads to formation of the corresponding saturated amines and alcohols, allylic amines and alcohols and imines and ketones or aldehydes. The regiochemistry of the reduction may be controlled by varying temperature, stoichiometry and reducing agent. Reaction of (PhCH=CHCH=NR)Fe(CO)3(0) (R=p-C6H4(CO)CH3 and m-C6H4(CO)CH3) with sodium borohydride leads to formation of (PhCH=CHCH=NR)Fe(CO)3(0) (R=p-C6H4(CHOH)CH3 and m-C6H4(CHOH)CH3) and demonstrates the ability of the tricarbonyliron(0) moiety to protect the coordinated 1-aza-1,3-diene against reduction by sodium borohydride allowing selective reduction of the free ketone function.