Vinylketene Silyl Research Articles

Brønsted Acid-Catalyzed, Enantioselective, Vinylogous Mannich Reaction of Vinylketene Silyl N,O-Acetals

Vinylketene silyl N, O-acetals undergo chiral phosphoric acid-catalyzed, vinylogous Mukaiyama-Mannich reactions with imines and afford delta-amino-alpha,beta-unsaturated amides in typically good yields, complete gamma-regioselectivity, and up to 92% ee with catalyst loadings of as low as 1 mol %. The Mannich products can be readily manipulated to furnish valuable synthetic intermediates.

Total Synthesis of Khafrefungin Using Highly Stereoselective Vinylogous Mukaiyama Aldol Reaction

[structure: see text] A convergent total synthesis of khafrefungin was accomplished on the basis of (1) the highly stereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using vinylketene silyl N,O-acetal and (2) syn-selective aldol reaction of enal 5a and ethyl ketone 6 followed by anti-dehydration under Mitsunobu conditions.

The First Total Synthesis of Trichostatin D.

Trichostatin D and 6-epi-trichostatin D have been stereoselectively synthesized through a remote stereoinduction with a chiral vinylketene silyl N,O-acetal and glycosylation of hydroxyimide under Mitsunobu conditions.

Remote Asymmetric Induction with Vinylketene Silyl N,O‐Acetal.

A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.

The first total synthesis of trichostatin D

Trichostatin D and 6- epi-trichostatin D have been stereoselectively synthesized through a remote stereoinduction with a chiral vinylketene silyl N, O-acetal and glycosylation of hydroxyimide under Mitsunobu conditions.

Remote Asymmetric Induction with Vinylketene SilylN,O-Acetal

A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.

Reactions of ketene silyl acetals with imine-complexes of titanium tetrachloride. New and convenient routes to 5,6-dihydro-2-pyridones and 5-amino-2-alkenoates

The reactions of vinylketene silyl acetals (VKSAs) with imine complexes of TiCl 4 give the corresponding 5,6-dihydro-2-pyridones and/or 5-amino-2-alkenoates in good to excellent yields. It is suggested that an addition-cyclization mechanism is operative for the formation of 5,6-dihydro-2-pyridones in this formal cyclocondensation reaction.

Coupling reactions of vinylketene silyl acetals promoted by titanium tetrachloride

Homo- and cross-couplings of vinylketene silyl acetals were found to be effectively promoted by titanium tetrachloride to give the corresponding unsaturated diesters in good yields. The reactions between two different ketene silyl acetate afforded the corresponding cross-coupling products in unexpectedly good selectivities.