Transacetalization of Diethyl Tartrate with Acetals of .alpha.-Dicarbonyl Compounds: A Simple Access to a New Class of C2-Symmetric Auxiliaries and Ligands

Abstract

A simple access to a new class of Cz-symmetric auxiliaries and ligands is based on the transacetalization of diethyl tartrate (1) with monoacetals of butane-2,3-dione in the key step. Acidcatalyzed reaction of 1 with 2 equiv of 3,3-diethoxybutan-2-one (2) gives the Cz-symmetric 1,4dioxane 7 in 88% yield. Reduction of 7 with LiAlH4 affords the crystalline diol 9. The structure of 7 was established from the X-ray structure of 9. Dioxane 7 was converted by standard methodology into the diphosphine 24 and the TARTROL 22. Reaction of 1 with 3,3-dimethoxybutan-2-one (3) in the presence of BFs-etherate gives in analogy to the formation of 7 the 1,4-dioxane 8. This compound was transformed into the diphosphine 25 and the TARTROL 23. The trans-diaxial relationship of the methoxy groups present in 8 could be deduced without X-ray analysis from the lH-NMR spectrum of 23.

Turning the Nitrogen Atoms of an Ar2P−CH2−N−N−CH2−PAr2 Motif into Uniquely Configured Stereocenters: A Novel Diphosphane Design for Asymmetric Catalysis

“…Figure retrieves the construction principle of the above‐mentioned diphosphane DIOP ( 2 , Figure ) in many newer diphosphanes from asymmetric catalysis studies: This is based on recognizing these compounds 5 , 6 , 7 , 8 , 9 , 10 11 , 12 , 13 , 14 , 15 , and 16 consistently as “2,3‐disubstituted‐1,4‐di‐unsubstituted‐1,4‐diphosphanes”.…”

A 1,2‐trans‐Selective Glycosyl Donor Bearing Cyclic Protection at the C‐2 and C‐3 Hydroxy Groups

“…First, we synthesized various thioglucoside donors bearing a 2,3‐ trans ‐fused ring by using the nonacyl cyclic protecting groups di‐ tert ‐butylsilylene (DTBS), butanediacetal (BDA), tetraisopropyldisiloxanylidene (TIPDS), and Xyln (Figure ). The BDA‐, TIPDS‐, and Xyln‐protected thioglucoside derivatives 1 – 3 were obtained with six‐, seven‐, and eight‐membered fused rings, respectively, through straightforward protection–deprotection of the hydroxy groups.…”

Chiral Diphosphane‐ and NHC‐Containing Ruthenium Catalysts for the Catalytic Asymmetric Arylation of Aldimines with Organoboron Reagents

“…[26] Making structural changes to the catalyst can lead to better results. [27] Previous work in our laboratory [28][29][30][31] and from other groups [32][33][34][35][36][37][38] has shown the applicability of the conformationally locked cyclic diacetal backbone in asymmetric synthesis and particularly in asymmetric catalysis. Chiral diamine 11 [35,36] (Scheme 2) was obtained from the commercially available diazide 10 through a simple metal-catalyzed hydrogenation.…”