4.3. Reaction Mechanism 2373 4.4. Asymmetric Synthesis 2374 4.5. Outlook 2374 5. Alternating Polymerization of Oxiranes and CO2 2374 5.1. Reaction Outlines 2374 5.2. Catalyst 2376 5.3. Asymmetric Polymerization 2377 5.4. Immobilized Catalysts 2377 6. Synthesis of Urea and Urethane Derivatives 2378 7. Synthesis of Carboxylic Acid 2379 8. Synthesis of Esters and Lactones 2380 9. Synthesis of Isocyanates 2382 10. Hydrogenation and Hydroformylation, and Alcohol Homologation 2382

Transformation of carbon dioxide.

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

Efficient and reliable amplification of chirality has borne its greatest fruit with transition metal-catalyzed reactions since enantiocontrol may often be imposed by replacing an achiral or chiral racemic ligand with one that is chiral and scalemic While the most thoroughly developed enantioselective transition metal-catalyzed reactions are those involving transfer of oxygen (epoxidation and dihydroxylation)1,2 and molecular hydrogen,3 the focus of this review is on the area of enantioselective transition metal-catalyzed allylic alkylations which may involve C-C as well as C-X (X ) H or heteroatom) bond formation4-9 The synthetic utility of transitionmetal-catalyzed allylic alkylations has been soundly demonstrated since its introduction nearly three decades ago10-21 In contrast to processes where the allyl moiety acts as the nucleophilic partner, we will limit our discussion to processes which result in nucleophilic displacements on allylic substrates (eq 1) Such reactions have been recorded with a broad

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Asymmetric Transition Metal-Catalyzed Allylic Alkylations.

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Palladium-catalyzed cross-coupling reactions in total synthesis.

A. Primary Alcohols as Nucleophiles 2931 B. Carboxylates as Nucleophiles 2931 C. Alkylations with Phenols 2932 IV. Nitrogen Nucleophiles in AAA Total Synthesis 2935 A. Alkylamines as Nucleophiles 2935 B. Azides as a Nucleophile 2936 C. Sulfonamide Nucleophiles 2937 D. Imide Nucleophiles 2938 E. Heterocyclic Amine Nucleophiles 2940 V. Sulfur Nucleophiles 2941 VI. Summary and Conclusions 2941 VII. Acknowledgment 2941 VIII. References 2942 I. Considerations for Enantioselective Allylic Alkylation

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Asymmetric transition-metal-catalyzed allylic alkylations: applications in total synthesis.

Remarkable Effect of Ethylene Gas in the Intramolecular Enyne Metathesis of Terminal Alkynes.

A method for nickel-catalyzed asymmetric carbon dioxide (CO2) incorporation via carbon−carbon bond formation was developed In the presence of a catalytic amount of Ni(acac)2 and MeO-MOP, various bis-1,3-dienes reacted with CO2 (1 atm) and a diorganozinc reagent (Me2Zn or Ph2Zn) to afford cyclic carboxylic acids in good yields (71−100%) and with high enantioselectivities (90−96% ee)

Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes.

Novel nickel-catalyzed carboxylation of bis-1,3-dienes using carbon dioxide (CO2) was investigated. In the presence of catalytic amounts of Ni(acac)2 and PPh3, various bis-1,3-dienes smoothly reacted with CO2 and an organozinc reagent (Et2Zn, Me2Zn, or Ph2Zn) under mild conditions. This catalytic carboxylation process was accompanied by carbocyclization of bis-1,3-diene followed by alkylation by an organozinc reagent to afford cyclic carboxylic acid derivatives in high yields with high regio- and stereoselectivities.

Novel Catalytic CO2 Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes

Asymmetric Synthesis of Isoindoline and Isoquinoline Derivatives Using Nickel(0)-Catalyzed [2 + 2 + 2] Cocyclization

Since the molybdenum and ruthenium car- bene complexes 1a and 1b were discovered by Schrock and Grubbs in 1990 and 1992, synthetic or- ganic chemistry has progressed with the use of these complexes as the catalyst for olefin metathesis. It was found that the ruthenium carbene complex was also effective for enyne metathesis, which occurs between an alkene and an alkyne. Intramolecular enyne meta- thesis gives various cyclic compounds having a 1,3- diene moiety and cross-metathesis of an alkene with an alkyne is a useful method for the synthesis of a compound having a diene moiety. Furthermore, dien- yne metathesis, ROM of cycloalkenynes or tandem reactions of enyne metathesis have been developed. Using these various enyne metatheses, complicated natural products have been synthesized via novel routes. The syntheses of natural products and related compounds using enyne metathesis are described.

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Miwako Mori

Papers

Remarkable Effect of Ethylene Gas in the Intramolecular Enyne Metathesis of Terminal Alkynes.

Highly enantioselective catalytic carbon dioxide incorporation reaction: nickel-catalyzed asymmetric carboxylative cyclization of bis-1,3-dienes.

Novel Catalytic CO2 Incorporation Reaction: Nickel-Catalyzed Regio- and Stereoselective Ring-Closing Carboxylation of Bis-1,3-dienes

Asymmetric Synthesis of Isoindoline and Isoquinoline Derivatives Using Nickel(0)-Catalyzed [2 + 2 + 2] Cocyclization

Synthesis of natural products and related compounds using enyne metathesis