Transition-Metal-Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

The cyclopropanation of nonactivated alkenes with inexpensive triisobutylaluminum (TIBA), in dibromomethane as solvent and reagent, is efficiently catalyzed by FeCl3 at ambient temperature. Catalytic amounts of CuI salts, CpTiCl3, and [CpFe(CO)2]2 are similarly effective. 2‐Methylpropane, generated...

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Bibliographic Details
Published in:European Journal of Organic Chemistry 2011-08, Vol.2011 (24), p.4623-4633
Main Authors: Brunner, Gerhard, Elmer, Susanne, Schröder, Fridtjof
Format: Article
Language:English
Subjects:
Alicyclic compounds
Alicyclic compounds, terpenoids, prostaglandins, steroids
Alkenes
Aluminum
Applied sciences
Aroma and flavouring agent industries
Biological and medical sciences
Carbenoids
Catalysis
Catalysts: preparations and properties
Chemical industry and chemicals
Chemistry
Essential oils, perfumes
Exact sciences and technology
Food industries
Fragrances
Fundamental and applied biological sciences. Psychology
General and physical chemistry
Organic chemistry
Preparations and properties
Regioselectivity
Solvent effects
Synthetic methods
Terpenoids
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
Washing products. Cosmetics and toiletries. Perfumes
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Summary:The cyclopropanation of nonactivated alkenes with inexpensive triisobutylaluminum (TIBA), in dibromomethane as solvent and reagent, is efficiently catalyzed by FeCl3 at ambient temperature. Catalytic amounts of CuI salts, CpTiCl3, and [CpFe(CO)2]2 are similarly effective. 2‐Methylpropane, generated after quench of excess TIBA can be trapped, and excess dibromomethane can be recycled, which makes the method industrially applicable. Solvent‐free DIBAH or TIBA reduction of unsaturated carbonyl compounds, followed by in situ TIBA cyclopropanation of the unsaturated aluminum alcoholates in dibromomethane give cyclopropyl alkanols. Dienols such as geraniol, linalool or nor‐radjanol are selectively cyclopropanated in their distal position, which allows the synthesis of flavor and fragrance compounds such as Δ‐citral, cis‐javanol, and 7‐methyl‐georgywood. Uncontrollable exothermic events are avoided due to relatively low reaction temperatures made possible by the catalysts and by the addition mode of the reagents.1 The cyclopropanation of nonactivatedalkenes with inexpensive triisobutylaluminum, in dibromomethane as solvent and reagent, is catalyzed by transition‐metal complexes such as FeCl3 or CpTiCl3 at ambienttemperature. Aluminum dienolates are cyclopropanated with high selectivity in their distal position and can be generated in situ. The method was applied to the synthesis of flavor and fragrance compounds.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.201100528