Stronger Brønsted Acids: Recent Progress.

Four-membered ring-containing spirocycles: synthetic strategies and opportunities.

Carbon-carbon (C-C) bonds form the backbone of many important molecules, including polymers, dyes and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavour relies heavily on the ability to form C-C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a chemical transformation that allows the facile construction of highly substituted and uniquely functionalized C-C bonds. Using a simple iron catalyst, an inexpensive silane and a benign solvent under ambient atmosphere, heteroatom-substituted olefins are easily reacted with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than 60 examples are presented with a wide array of substrates, demonstrating the chemoselectivity and mildness of this simple reaction.

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Functionalized olefin cross-coupling to construct carbon–carbon bonds

Recent developments in catalytic asymmetric aldol reactions have been summarized. Enantioselective aldol reactions are important methods to synthesize β-hydroxy carbonyl compounds in optical pure form, and as such, numerous successful chiral catalysts were designed and applied for asymmetric aldol reactions. This review article is organized under the categories of: (1) catalytic enantioselective aldol reactions of preformed enolates, (2) catalytic enantioselective direct-type aldol reactions using chiral metal catalysts, (3) catalytic enantioselective direct-type aldol reactions using organocatalysts, (4) catalytic enantioselective aldol reactions in aqueous media. Examples of the aldol reactions that employ simple carbonyl compounds will be also the focus of this review.

Catalytic enantioselective aldol reactions

A zerovalent copper- and cobalt-catalyzed direct coupling of the sp3 α-carbon of alcohols with alkenes and hydroperoxides was developed in which the hydroperoxides acted as radical initiator and then coupling partner. 1,3-Enynes and vinylarenes underwent alkylation–peroxidation to give β-peroxy alcohols and β-hydroxyketones correspondingly with excellent functional group tolerance. The resulting β-peroxy alcohols could be further transformed into β-hydroxyynones and propargylic 1,3-diols.

Copper- and cobalt-catalyzed direct coupling of sp(3) α-carbon of alcohols with alkenes and hydroperoxides.

A directed cross-aldol reaction of silyl enol ethers with carbonyl compounds, such as aldehydes and ketones, promoted by a Lewis acid, a reaction which is now widely known as the Mukaiyama aldol reaction. It was first reported in 1973, and this year marks the 40th anniversary. The directed cross-aldol reactions mediated by boron enolates and tin(II) enolates also emerged from the Mukaiyama laboratory. These directed cross-aldol reactions have become invaluable tools for the construction of stereochemically complex molecules from two carbonyl compounds. This Minireview provides a succinct historical overview of their discoveries and the early stages of their development.

The Mukaiyama aldol reaction: 40 years of continuous development.

Intermolecular [4 + 2] cycloaddition between 3-alkoxycyclobutanones and aldehydes or ketones by the activation with boron trifluoride etherate is reported. The carbonyl compounds are inserted into the less substituted C2−C3 bond of the cyclobutanone ring of 6-alkyl-2-oxabicyclo[4.2.0]octan-7-ones to afford 1-alkyl-5,7-dioxabicyclo[4.4.0]decan-2-one derivatives regioselectively (>99:1) and diastereoselectively. On the other hand, [4 + 2] cycloaddition of 3-ethoxy-2,2-dialkylcyclobutanones at low temperature proceeds at the more substituted C2−C3 bond to yield 3,3-dialkyl-6-ethoxy-2,3,5,6-tetrahydro-4H-pyran-4-one derivatives with high regioselectivities. This [4 + 2] cycloaddition is developed into a one-pot synthesis of tri- or tetrasubstituted dihydro-γ-pyrones from 3-ethoxycyclobutanones which are readily prepared from acid chloride and ethyl vinyl ether. The two regioselectivities observed in ring-opening of cyclobutanones can ascribe to thermodynamic stabilities of zwitterionic intermediates generated...

https://pubs.acs.org/doi/pdf/10.1021/ja806907a

Lewis Acid-Catalyzed Intermolecular [4 + 2] Cycloaddition of 3-Alkoxycyclobutanones to Aldehydes and Ketones

40 Jahre Mukaiyama‐Aldolreaktion: eine Erfolgsgeschichte

Stereoselective synthesis of cis and trans-fused 3a-aryloctahydroindoles using cyclization of N-vinylic α-(methylthio)acetamides: synthesis of (−)-mesembrane

Jun‐ichi Matsuo

Papers

The Mukaiyama aldol reaction: 40 years of continuous development.

Lewis Acid-Catalyzed Intermolecular [4 + 2] Cycloaddition of 3-Alkoxycyclobutanones to Aldehydes and Ketones

40 Jahre Mukaiyama‐Aldolreaktion: eine Erfolgsgeschichte

Stereoselective synthesis of cis and trans-fused 3a-aryloctahydroindoles using cyclization of N-vinylic α-(methylthio)acetamides: synthesis of (−)-mesembrane

The Mukaiyama Aldol Reaction: 40 Years of Continuous Development