Generation of a Silylethylene−Titanium Alkoxide Complex. A Versatile Reagent for Silylethylation and Silylethylidenation of Unsaturated Compounds

Abstract

(Trimethylsilyl)ethylene-titanium alkoxide complex (1) was generated from trimethyl(vinyl)silane, Ti(O-i-Pr)(4), and i-PrMgCl as a preformed alkene-titanium complex and reacted with several unsaturated compounds such as aldehyde, imine, other vinylsilane, and acetylene to give the corresponding coupling products 4a-f, 6, 8, and 10a-d in a regioselective manner. Both of the two carbon-titanium bonds of the complex 1 reacted successively with esters to afford silylcyclopropanols 11a-j, 13, and 15, some synthetic applications of which were illustrated in the preparation of beta-silyl ketones 16 and cyclopropenes 17. Asymmetric addition of 1 to a chiral acyloxazolidinone 19 gave optically active cyclopropanol (+)-11a of 50% ee.

Convenient Route to 2‐(Trialkylstannyl)cyclopropylamines and Their Application in Palladium‐Catalyzed Cross‐Coupling Reactions

“…It is also known that silyl-substituted titanacyclopropane intermediates react with aldehydes only according to insertion mode a. [10] After all, the high diastereoselectivity observed in the conversion of N,N-dialkylformamides with vinylstannanes to 2-stannylcyclopropylamines may simply be due to the steric bulk of the trialkylstannyl group. A control experiment with 3,3-dimethylbut-1-ene (tert-butylethene) also gave only trans-N,N-dibenzyl-2-tert-butylcyclopropylamine, but in poor yield (19%) and an impure state.…”

“…propylamine (3a) with ethyl trans-3-iodoacrylate (9) and subsequent rearrangement to yield ethyl cis-5-(dibenzylamino)cyclopent-2-enecarboxylate (10) This coupling-rearrangement sequence constitutes a diastereoselective synthesis of an interesting β-aminocyclopentenecarboxylic acid in a protected form. The facility of this stereoselective approach to a synthetically useful cyclopentene derivative warrants further investigations into coupling reactions of the readily available aminocyclopropylstannanes, with, for example, various functionally substituted iodoalkenes [14a] and β-iodo-substituted α,β-unsaturated carbonyl compounds.…”

Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

“…Trialkylvinylsilanes [41,42] and trialkylvinylstannanes [43] have also been successfully subjected to titaniummediated intermolecular hydroxycyclopropanation reactions. Intramolecular hydroxycyclopropanation of ω-unsaturated carboxylic esters have readily afforded cyclopropanols fused to ordinary carbocyclic or heterocyclic rings.…”

X‐Ray Structure Analyses of syn/anti‐Conformers of N‐Furfuroyl‐, N‐Benzoyl‐, and N‐Picolinoyl‐Substituted (2R)‐Bornane‐10,2‐sultam Derivatives

“…4) are very similar and express the more stable anti-s-trans conformer, as confirmed by calculations. The main difference arises from the N(2) lp, which points either above O(1) in structure 2cA 8 ) or in-between O(1) and O(2) in 7 ) Although erroneously mentioned in reference [11], 2b was neither prepared nor described in [12], nor elsewhere. structure 2cB, while the third one, 2cC (Fig.…”