[1,2]-Wittig rearrangement of enantio-defined α-alkoxyalkyllithiums: Structural requirement and steric course at the Li-bearing terminus

A removable functional group strategy for regiodivergent Wittig rearrangement products

[1,2] and [2,3] Wittig rearrangements are competing reaction pathways, often leading to uncontrollable product distribution. We employ a single removable functional group to fulfill the dual role of attaining a reversible [2,3] and stabilizing radical intermediate for the [1,2] path to obtain both the Wittig products selectively for a broad range of substrates.

Radical Cage Effects: The Prediction of Radical Cage Pair Recombination Efficiencies Using Microviscosity Across a Range of Solvent Types

This study reports a method for correlating the radical recombination efficiencies (F_cP) of geminate radical cage pairs to the properties of the solvent. Although bulk viscosity (macroviscosity) is typically used to predict or interpret radical recombination efficiencies, the work reported here shows that microviscosity is a much better parameter. The use of microviscosity is valid over a range of different solvent system types, including nonpolar, aromatic, polar, and hydrogen bonding solvents. In addition, the relationship of F_cP to microviscosity holds for solvent systems containing mixtures of these solvent types. The microviscosities of the solvent systems were straightforwardly determined by measuring the diffusion coefficient of an appropriate probe by NMR DOSY spectroscopy. By using solvent mixtures, selective solvation was shown to not affect the correlation between F_cP and microviscosity. In addition, neither solvent polarity nor radical rotation affects the correlation between F_cP and the microviscosity.

alpha-Substituted acylsilanes via a highly selective [1,4]-Wittig rearrangement of alpha-benzyloxyallylsilane

alpha-Benzyloxyallylsilane undergoes efficient [1,4]-Wittig rearrangement to generate an enolate intermediate that can be trapped with various electrophiles, thereby providing a new synthetic approach to substituted acylsilanes.

Novel [1,2]- and [2,3]-Wittig rearrangements of alpha-benzyloxy beta-CF(3)-beta-lactam enolates

[reaction: see text] alpha-Benzyloxy alpha-CF(3)-beta-lactams are shown to offer the first examples of the enolate [1,2]- and enolate ortho-[2,3]-Wittig rearrangements which provide a unique entry to the alpha-benzyl-alpha-hydroxy lactams and the alpha-aryl-alpha-hydroxy lactams, respectively. Both products are potential precursors of new trifluoromethyl isoserines, and the latter is not accessible via the usual alkylation methodology.