R. Hartmann

Bio: R. Hartmann is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 65 citations.

Ruthenium‐based metathesis initiators: Development and use in ring‐opening metathesis polymerization

Abstract: For many years, olefin metathesis has been a central topic of industrial and academic research because of its great synthetic utility. The employed initiators cover a wide range of compounds, from simple transition-metal salts to highly sophisticated and well-defined alkylidene complexes. Currently, ruthenium-based catalysts are at the center of attention because of their remarkable tolerance toward oxygen, moisture, and numerous functionalities. This article focuses on recent developments in the field of ring-opening metathesis polymerization using ruthenium-based catalysts. ruthenium-based initiators and their applications to the preparation of advanced polymeric materials are briefly reviewed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2895–2916, 2002

A Chemical Investigation of the Volatile Constituents of East Indian Sandalwood Oil (SantalumalbumL.)

Abstract: Distillation foreruns from East Indian sandalwood oil (Santalum albumL.), representing 5–8% of the oil, have been investigated using fractional distillation, preparative column chromatography, gas liquid chromatography (GLC.), and chemical treatments. This allowed the isolation and characterization by their spectral data of 46 compounds. 32 of them were newly identified sandalwood oil constituents including 4 novel substances: santalone (2), 4-methylcyclohexa-1,3-dien-1-yl methyl ketone (4), 5,6-dimethyl-5-norbornen-exo-2-ol (7), and (E)-5-(2,3-dimethyl-3-nortricyclyl)-pent-3-en-2-one (20). The other constituents identified were 1-furfuryl-pyrrole (10) and 10 phenols accompanied by 17 terpene and sesquiterpene derivatives. Endo-2,endo-3-dimethyl-norbornan-exo-2-ol (6), an α-santenol (z), precursor, was present in the last group of constituents. The compounds 2, 4, 6, 7, 20 have been synthesized as well as another novel constituent, endo-2-mythyl-3-methylidene-norbornan-exo-2-ol (5).

1 – Stereoselective Alkylation Reactions of Chiral Metal Enolates

Abstract: I. Prologue 2 II. Selective Enolate Formation 6 A. Introduction 6 B. Determination of Enolate Geometry 12 C. Enolization of Acyclic Carbonyl Derivatives 14 III. Enolate Structure 21 IV. Transition-State Control Elements 23 A. Introduction 23 B. Stereoelectronic Effects 25 C. Steric Effects 29 V. Intraannular Chirality Transfer 30 A. Introduction 30 B. Exocyclic Enolates 31 C. Five-Membered Endocyclic Enolates 37 D. Enolates in the Norbornyl Ring System 45 E. Six-Membered Endocyclic Enolates 50 F. Asymmetric Synthesis of Chiral Synthons via Intraannular Chirality Transfer 73 VI. Chelate-Enforced Intraannular Chirality Transfer 80 A. Introduction 80 B. Asymmetric Synthesis of Chiral Synthons via Chelate-Enforced Intraannular Chirality Transfer . . . . 83 VII. Extraannular Chirality Transfer 93 VIII. Conclusions 100 References 101

Total syntheses of sandalwood fragrances: (Z)- and (E)-β-santalol and their enantiomers, ent-β-santalene

Abstract: Via asymmetric Diels-Alder reactions, large scale preparations of enantiomerically pure norbornane-2-carboxylic acids were carried out. Oxidative degradation furnished 2-norbornanone and 3-methyl-2-norbornanone which gave the title compounds via stereoselective alkylations, subsequent Wittig reactions and reductions.

Alkylations of Enols and Enolates

Abstract: The α-alkylation of carbonyl compounds by their conversion into nucleophilic enolates or enolate equivalents and subsequent reaction with electrophilic alkylating agents provides one of the main avenues for regio- and stereo-selective formation of carbon–carbon σ-bonds.1–6 Classical approaches to α-alkylation typically involve the deprotonation of compounds containing doubly activated methylene or methine groups and having pKa values of 13 or below by sodium or potassium alkoxides in protic solvents. Since these conditions lead to monoenolates derived from deprotonation only at the α-site of the substrate, the question of the regioselectivity of C-alkylation does not arise (however, there is competition between C- and O-alkylation in certain cases). In more recent years, dienolates of β-dicarbonyl compounds have been utilized in γ-alkylations with excellent success.