Anti-selective aldol reactions with titanium enolates of N-glycolyloxazolidinethiones.
نویسندگان
چکیده
[reaction: see text] A highly diastereoselective anti aldol addition utilizing a variety of N-glycolyloxazolidinethiones has been developed. Enolization of an N-glycolyloxazolidinethione with titanium (IV) chloride and (-)-sparteine followed by addition of an aldehyde activated with additional TiCl(4) resulted in highly anti-selective aldol additions, typically with no observable syn isomers. Allyl-protected glycolates demonstrated the highest levels of selection and yields, although O-benzyl and O-methyl glycolyloxazolidinethiones also performed well.
منابع مشابه
Stereoselective Acetate Aldol Reactions
The stereochemical control of aldol reactions from unsubstituted enolor enolatelike species, what are known as acetate aldol reactions, has been a matter of concern for nearly 30 years [1, 2]. Indeed, pioneering studies soon recognized that the asymmetric installation of a single stereocenter in such aldol reactions was much more demanding than the simultaneous construction of two new stereocen...
متن کاملHighly Diastereoselective Aldol Reactions of Chiral Methyl Ketones
Diastereoselective aldol additions have emerged as one of the most efficient and versatile methods available for preparing a wide range of optically active compounds.l Very high diastereoselectivities have been reported for aldol reactiona involving chiral enolates derived from a-ethylor higher alkyl-substituted ketone derivatives. By contrast, relatively few examples of highly diastereoselecti...
متن کامل1,5-asymmetric induction in boron-mediated beta-alkoxy methyl ketone aldol addition reactions.
This article presents studies that illustrate beta-alkoxy methyl ketone-derived boron enolates undergo diastereoselective aldol addition to afford the 1,5-anti diol relationship. The stereochemical outcome of this reaction is documented to be general for a variety of beta-alkoxy methyl ketone analogues and aldehyde partners. The double stereodifferentiating reactions of these enolates with chir...
متن کاملThe Mukaiyama aldol reaction: 40 years of continuous development.
A directed cross-aldol reaction of silyl enol ethers with carbonyl compounds, such as aldehydes and ketones, promoted by a Lewis acid, a reaction which is now widely known as the Mukaiyama aldol reaction. It was first reported in 1973, and this year marks the 40th anniversary. The directed cross-aldol reactions mediated by boron enolates and tin(II) enolates also emerged from the Mukaiyama labo...
متن کاملTitanium enolates of thiazolidinethione chiral auxiliaries: versatile tools for asymmetric aldol additions.
[formula: see text] Asymmetric aldol additions using chlorotitanium enolates of thiazolidinethione propionates proceed with high diastereoselectivity for the "Evans" or "non-Evans" syn product depending on the nature and amount of the base used. With (-)-sparteine as the base, selectivities of 97:3 to > 99:1 were obtained for the Evans syn products with 2 equivalents of base and for the non-Eva...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Organic letters
دوره 5 4 شماره
صفحات -
تاریخ انتشار 2003