Trialkyltin enolate

This computational study revealed the mechanism of the reaction between trialkyltin enolates and aldehydes or organic halides, both without and with coordinating ligands. High coordination of trialkyltin enolates causes an increase of their nucleophilicity and decrease of Lewis acidity of the tin center, which control the course of reaction . In the reaction of tin enolates with aldehydes, a noncoordinated tin enolate gives a cyclic TS in sled conformation whereas an acyclic TS leading to deactivation of the process is shown in the case of a highly coordinated enolate. Both theoretical and experimental results of... 

Alkanes can be nitrosated photochemicaUy, by treatment with NOCl and UV light. For nitration at an activated carbon, see 12-9. Trialkyltin enol ethers (C=C-0-SnR3) react with PhNO to give a-(A-hydroxylamino)ketones. ° ... 

There is a growing interest in the tin enolates that can be prepared by treating enol acetates with trialkyltin methoxides, e.g. (193),... 

Trialkylstannyl enolates can be prepared from enol acetates by reaction with trialkyltin alkoxides and are sufficiently reactive to add to aldehydes. Uncatalyzed addition of trialkylstannyl enolates to benzaldehyde shows anti stereoselectivity.31... 

In the general context of donor/acceptor formulation, the carbonyl derivatives (especially ketones) are utilized as electron acceptors in a wide variety of reactions such as additions with Grignard reagents, alkyl metals, enolates (aldol condensation), hydroxide (Cannizzaro reaction), alkoxides (Meerwein-Pondorff-Verley reduction), thiolates, phenolates, etc. reduction to alcohols with lithium aluminum hydride, sodium borohydride, trialkyltin hydrides, etc. and cyloadditions with electron-rich olefins (Paterno-Buchi reaction), acetylenes, and dienes.46... 

Tin(iv) enolates are normally generated by transmetallation from lithium enolates with trialkyltin halides or transesterification between enol acetates with trialkyltin alkoxides.220 Other types of generation systems are described below. 

The formal elimination of trialkyltin hydrides from enol systems has been very recently devised by Corey and Wollenberg to prepare terminal acetylenes (equation 92) and to introduce the ethynyl group into the -position of a, -unsaturated ketones. As equation (93) shows this may lead to the introduction of an ethynyl group into an angular position d . The preparation of the reagent 31 has been described . 

Tin(IV) enolates are generated by the reaction of lithium enolates with trialkyltin chlorides. The best stereoselectivity in the aldol reaction with tin(IV) enolates has been achieved by employing tri-phenyltin chloride. Syn/erythro aldol products were predominantly produced irrespective of the geometry of the starting enolates (Scheme 39). However, the aldol condensation via the enolate derived from norbomanone gave the anti/threo product predominantly (Scheme 40). ... 

Unbranched and substituted alkyl carbamates, such as 146 or 147 [62,88] do not cause any problems in the deprotonation step. Deuteration (with CH3OD or dissolved CH3CO2D), methoxycarbonylation (gaseous CO2, followed by diazomethane after work-up or methyl chloroformate), alkylation with methyl iodide, substitution with trialkylsilyl chlorides, trialkyltin chlorides and even tri-methyllead bromide, addition onto aldehydes and ketones, and acylation with acid chlorides or esters, all proceed without difficulties. Although a ketone is formed in the latter reactions, which is at least 15 orders of magnitude thermodynamically more acidic than the alkyl carbamate we never observed enolate formation, racemization or epimerization - with one exception it occurred to some extent after formylation with formate esters [79]. 

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