Michael R. Metzler

Coupling reactions of diterpenoid η2-tetracarbonylmanganese complexes with alkynes

Abstract A number of tetracarbonylmanganese complexes derived from podocarpic acid ( 1 ) have been coupled with acetylene or diphenylacetylene to give steroidal analogues in high yield. Several modes of activating these manganese complexes towards coupling reactions were investigated, including oxidative decarbonylation at room temperature and thermal promotion.

Reactions with alkenes of η2-7-oxotetracarbonylmanganese complexes derived from diterpenoids

Abstract A number of activated 7-oxotetracarbonylmanganese(I) complexes derived from podocarpic acid ( 1 ) and from dehydroabietic acid have been coupled with alkenes to give C(14) functionalised derivatives in high yields. Some coupling reactions resulted in cyclization to C(7), forming 4 H -acephenanthrylene derivatives in moderate yields. Several modes of activating these manganese complexes towards coupling reactions were investigated; these included oxidative decarbonylation at room temperature, thermal promotion, and palladium-mediation.

Reactions of η2-13-acyltetracarbonylmanganese complexes derived from podocarpic acid with alkenes; cyclopentaannulation of ring C

Abstract A number of 13-acyltetracarbonylmanganese( I ) complexes derived from podocarpic acid ( 1 ) have been coupled with alkenes to give steroidal analog

Synthesis and reactions of [(((η6)-2-acylaryl)-C,O)tetracarbonylmanganese]-tricarbonylchromium complexes: enhancement of diastereoselection during cyclopentaannulation

Abstract Cyclomanganation reactions of [( η 6 )-acylaryl]tricarbonylchromium complexes have been investigated. Three novel heterobimetallic complexes have been synthesised in moderate to good yield, with one being characterised by X-ray crystallography. Several modes of activating these bimetallic complexes towards coupling reactions with substituted alkenes and alkynes were investigated, including oxidative decarbonylation at room temperature, and thermal promotion. The stereochemistry of one of the cyclopentaannulated adducts has been established by X-ray crystallography. Thermal displacement of one of the CO ligands of the bimetallic complex 27 in the presence of PPh 3 afforded a single adduct, the structure of which was established by X-ray crystallography. The chemistry of this novel bimetallic system was investigated.

Organomanganese complexes of podocarpic acid derivatives

Abstract Cyclomanganation reactions of podocarpic acid derivatives containing aldehyde, ketone, ester, or oxime groups as directing functionalities have been investigated. Attempted complexation of amide-containing ligands proved generally to be unsuccessful whereas benzylic ketones gave their corresponding tetracarbonyl complexes in high yields. Complexation of ligands containing either two potential sites for manganation or two potential ligating groups were also investigated and the structures of the isolated complexes established unequivocally by NMR or X-ray crystallogr

Cyclomanganation of diterpenoids; functionalization of C14

Abstract Orthomanganated complexes have been made from carbonyl derivatives of the ring-C aromatic diterpenoids podocarpic acid and dehydroabietic acid. Activation of these complexes with Me 3 NO followed by coupling reactions with various substituted alkenes results in efficient substitution at C14. In some cases a tetracyclic indenol derivative is formed directly. Insertion of an alkyne also leads to cyclopentaannulation.

Synthesis and reactivity of the pentamethylcyclopentadienyl iron acetyl complex [(η5-C5Me5)Fe(CO)(PPh3)COMe]

Abstract (RS)-[(η5-C5Me5)Fe(CO)(PPh3)COMe] (1) was synthesised from [(η5-C5Me5)Fe(CO)2]2 (3) in three steps with an overall yield of 28%. The lithium enolate from 1 was alkylated with methyl iodide and benzyl bromide to give 11 and 12 in 94 and 97% yields respectively. The corresponding diethylaluminium enolate derived from 1 reacted with high stereoselectivity with benzaldehyde whereas no selectivity was observed with the lithium enolate. A single crystal X-ray structure analysis of (RS)-[(η5-C5Me5)Fe(CO) (PPh3)COCH2CH2Ph] (12) is reported.

Synthesis and reactions of ν2-(2-formylphenyl)tetracarbonylmanganese(I) complexes; cyclopentaanulation of a diterpenoid

Abstract Reaction of tetracarbonylmangenese(I) complexes derived from a diterpenoid aryl aldehyde or aryl methyl ketone with acetylene or ethylene leads to cyclopentaannulation to give 1H-inden-1-ols or 1H-indan-ols, respectively.

Kinetic resolution of the chiral iron acetyl complexes [Fe(CO)(η5-C5H5)(L)COCH3][L = PPh3, P(p-tolyl)3]via aldol reactions with camphor

The chiral iron acetyl complexes [Fe(CO)(η5-C5H5)(L)COCH3][L = PPh3, P(p-tolyl)3] have been kinetically resolved via aldol reactions involving their derived lithium enolates and camphor in the presence of lithium chloride. With (1R)-(+)-camphor the faster reacting iron acetyl enantiomer had the (S)-configuration allowing the (R)-iron acetyls to be obtained after recovery of starting material and crystallisation. The corresponding (S)-iron acetyls can be obtained by a base-promoted reverse aldol reaction of the isolated products. A mechanistic rationale for the high enantiomeric discrimination is proposed which involves a chelation-controlled chair transition state with a disfavourable 1-methyl to cyclopentadienyl interaction in the mismatched pairing.

ORGANOIRON COMPLEXES OF PODOCARPIC ACID DERIVATIVES

Abstract Treatment of the non-conjugated 1,4-dienes obtained by Birch reduction of podocarpa-8,11,13-trien-19-ol ( 2 ) and 12,19-dimethoxypodocarpa-8,11,13-triene ( 4 ) with Fe 3 (CO) 12 leads (albeit in low yields) in each case to a mixture of η 4 -1,3-diene iron complexes whose structures have been assigned by NMR spectroscopy. One of these complexes has been successfully converted into a catinic η 5 -dienyl iron salt ( 35 ) by treatment with acid. Attempted complexation of the 1,4-dienol ethers by treatment with a variety of sources of Fe(CO) 3 under mild conditions has led to the conclusion that prior conversion of a 1,4-dienol ether into a 1,3-dienol ether is necessary for success. In model studies, treatment of 1-methoxy-3,4-dimethyl-cyclohexa-1,4-diene ( 9 ) with Fe 3 (CO) 12 has given η 4 -diene and subsequently η 5 -dienyl iron complexes.