Asymmetric 1,3-Dipolar Cycloaddition Reactions

We present an approach to couple ab initio quantum mechanical geometry optimiuzations with molecular mechanical optimizations, with the added capability to carry out molecular dynamics simulations of the systems to earch for new local minima. The approach is applied to the aqueous solution CH3Cl + Cl− exchange reaction and the gas phase protonation of polyethers.

A combined ab initio quantum mechanical and molecular mechanical method for carrying out simulations on complex molecular systems: Applications to the CH3Cl + Cl− exchange reaction and gas phase protonation of polyethers

Transition metal chemistry of cyclopropenes and cyclopropanes.

Construction of enantiopure pyrrolidine ring system via asymmetric [3+2]-cycloaddition of azomethine ylides.

The addition of C-nucleophiles such as Grignard reagents or enolates to chiral α- or β-alkoxy aldehydes or ketones creates a new center of chirality and is therefore diastereogenic. In order to control stereoselectivity, two strategies have been developed: (1) Use of Lewisacidic reagents which form intermediate chelates, these being attacked stereoselectively from the less hindered side (chelation control); (2) use of reagents incapable of chelation, stereoselective attack being governed by electronic and/or steric factors (non-chelation control). Generally, the two methods lead to the opposite sense of diastereoselectivity. It is possible to predict the outcome by careful choice of organometallic reagents containing elements such as Li, Mg, B, Si, Sn, Cu, Zn, or Ti.

For corrigendum see DOI:10.1002/anie.198407461

Chelation or Non‐Chelation Control in Addition Reactions of Chiral α‐ and β‐ Alkoxy Carbonyl Compounds [New Synthetic Methods (44)]

Stereoselective nitrile oxide cycloadditions to chiral allyl ethers and alcohols. The inside alkoxy effect

Synthesis of amino sugars via isoxazolines: DL- and D-lividosamine (2-amino-2,3-dideoxy-ribo-hexose) derivatives from 4-vinyl-1,3-dioxolanes and nitroacetaldehyde acetals

[3+2]-Cycloaddition of nitrile oxides with alkenes, modification of isoxazoline intermediates, and subsequent cleavage give rise to a variety of functionalized acyclic structures. Each step may be used to diastereoselectively increase the number of chiral centres. Application of this concept to the synthesis of natural amino polyols, amino sugars and hydroxy amino acids is discussed.

R. Schohe

Papers

Stereoselective nitrile oxide cycloadditions to chiral allyl ethers and alcohols. The inside alkoxy effect

Synthesis of amino sugars via isoxazolines: DL- and D-lividosamine (2-amino-2,3-dideoxy-ribo-hexose) derivatives from 4-vinyl-1,3-dioxolanes and nitroacetaldehyde acetals

Isoxazolines‐Key Intermediates For Syntheses of Some Naturally Occuring Amino Compounds

Asymmetric induction in nitrile oxide cycloadditions to 3-butene-1,2-diol and derivatives

Isoxazolines - key intermediates for syntheses of some naturally occuring amino compounds