CO insertion in lithiated diene–tricarbonyliron complexes

Abstract

Lithiated 1,3-diene-iron complexes undergo a CO insertion in the presence of trimethyl phosphite via a ferrate intermediate to give 3-formyl or 3-acetyl-1,3-diene-Fe(CO)(2)P(OMe)(3) complexes. Formylation proceeds when the reaction is quenched by a strong Brønsted acid, whereas the ketone is obtained after the treatment with iodomethane.

Iron Dienylphosphate Tricarbonyl Complexes as Water-Soluble Enzyme-Triggered CO-Releasing Molecules (ET-CORMs)

“…All compounds synthesized were fully characterized by the common spectroscopic methods (IR, NMR, MS), and the structures of rac - 6b , rac - 6e , rac - 7d , and rac - 7e were additionally confirmed by single-crystal X-ray diffraction analysis. Similar to the situation in (acyloxycyclohexadiene)Fe(CO) 3 complexes, ,, the Fe(CO) 3 -complexed diene unit of the phosphoryloxy-substituted derivatives reported here is virtually planar and the cyclohexadiene ring adopts a boat-type conformation with torsion angles between 41.6(4) and 44.7 (3)° for the endocyclic C sp 2 –C sp 3 bonds of rac - 6b , rac - 7d , and rac - 7e . The torsion angles in each of these molecules do not differ more than 1.7(4)°, corresponding to an almost undistorted (symmetric) boat conformation of the cyclohexadiene ring.…”

“…In contrast to an earlier method (based on the deprotonation of nonconjugated 3-cyclohexen-1-one with lithium tetramethylpiperidide (LiTMP) or lithium diisopropylamide (LDA) and subsequent reaction with diethyl chlorophosphate), we succeeded in regioselectively generating the required dienolate starting from 2-cyclohexen-1-one ( 8 ) by deprotonation with lithium hexamethyldisilazide (LiHMDS) in the presence of tripyrrolidinophosphoric acid triamide (TPPA) as a cosolvent. Complexation of the dienylphosphate 9 under established conditions ((η 4 -benzylideneacetone)Fe(CO) 3 in toluene) yielded the desired complex rac - 6a in good overall yield (Scheme ).…”

“…Racemic complexes of type 7 (substituted at the “inner” position) had been reported before by Okauchi et al (and used in directed lithiation reactions), who prepared such compounds either through complexation of the corresponding dienes or by O-phosphorylation of an isolated (dienol)Fe(CO) 3 complex . Here, we describe the synthesis of (dienylphosphate)Fe(CO) 3 complexes of both type 6 and type 7 using a different approach, which is based in both series on the phosphorylation of an in situ generated (dienol)Fe(CO) 3 intermediate.…”

Unprecedented formation of η4-(vinylketene)iron complexes from η4-(diene)iron complexes and aromatic compounds in the presence of a Lewis acid

“…3,4 Although a number of Z 4 -(vinylketene)iron complexes have been prepared from a variety of compounds, 4 there are no reports on the preparation of Z 4 -(vinylketene)iron complexes from Z 4 -(diene)iron complexes. As part of our continuing interest in the chemistry of Z 4 -(diene)iron complexes, 5,6 we have been investigating their reaction in the presence of a Lewis acid. It is known that Z 4 -(diene)iron complexes are reactive towards electrophilic reagents.…”