Hetero asymmetric

Catalytic asymmetric hetero-Diels-Alder addition of carbonyl compounds 99ACR605. 

Metal-catalyzed asymmetric hetero Diels-Alder reactions of unactivated dienes with glyoxylates 98PAC1117. 

Lewis-acid-catalyzed asymmetric hetero-Diels-Alder cycloaddition of a 1-thiabuta-1,3-diene with chiral A/-acryloyl and A/-crotonyl oxazolidinone dienophile [105]... 

Jorgensen K. A. Catalytic Asymmetric Hetero-Diels-Alder Reactions of Carbonyl... 

Ooi T., Maruoka, K. Hetero-Diels-Alder and related reactions in Compr. Asymmetric Catal. I-III 1999 3 1237 Eds. Jacobsen EN, Pfaltz A and Yamamoto H, Pb. Springer-Verlarg, Berlin... 

Keywords catalytic asymmetric hetero-Diels-Alder reaction... 

Johannsen M., Yao S., Graven A., Jorgensen K. A. Metal-Catalyzed Asymmetric Hetero-Diels-Alder Reactions of Unactivated Dienes With Glyoxylates Pure Appl. Chem. 1998 70 1117-1122... 

Waldmann H. Asymmetric Hetero Diels-Alder Reactions Synthesis 1994 535-551... 

A successful case study for asymmetric nitrogen oxidation was reported for a series of (hetero)aromatic tertiary amines. High diastereoselectivity was observed for the enzyme-mediated oxidation of S-(—)-nicotine by isolated CHMOAdneto to give the corresponding ds-N-oxide [215]. The stereoselectivity of this biooxidation was complementary to the product obtained by flavin M O (FM O) from human li ver (trows-selective [216]) as well as unspecific oxidations by FMOs from porcine and guinea pig liver. 

Associated to copper(II) pre-catalysts, bis(oxazolines) also allowed the asymmetric Diels-Alder and hetero Diels-Alder transformations to be achieved in nearly quantitative yield and high diastereo- and enantioselectivities. Optically active sulfoximines, with their nitrogen-coordinating site located at close proximity to the stereogenic sulfur atom, have also proven their efficiency as copper ligands for these asymmetric cycloadditions. Other precursors for this Lewis acid-catalyzed transformation have been described (e.g., zinc salts, ruthenium derivatives, or rare earth complexes) which, when associated to bis(oxazolines), pyridine-oxazolines or pyridine-bis(oxazolines), led to efficient catalysts. 

The use of chiral bis(oxazoline) copper catalysts has also been often reported as an efficient and economic way to perform asymmetric hetero-Diels-Alder reactions of carbonyl compounds and imines with conjugated dienes [81], with the main focus on the application of this methodology towards the preparation of biologically valuable synthons [82]. Only some representative examples are listed below. For example, the copper complex 54 (Scheme 26) has been successfully involved in the catalytic hetero Diels-Alder reaction of a substituted cyclohexadiene with ethyl glyoxylate [83], a key step in the total synthesis of (i )-dihydroactinidiolide (Scheme 30). 

Several groups have reported the use of rare earth complexes as catalysts for asymmetric Diels-Alder reaction. Qian and Wang described thus the preparation and use of Yb complexes chelated by Pr-PyBOx to successfully achieve the hetero-Diels-Alder reaction of methyl glyoxylate with Danishefsky s diene in 77% ee and 73% yield (Scheme 37) [98]. 

Bolm et al. [108] prepared a C2-symmetric bis (sulfoximine) as ligand for the copper-catalyzed hetero-Diels-Alder reaction. The stereogenic sulfur atom being located near the AT-coordinating atom, these structures were assumed to be promising for asymmetric catalysis. Their Hgand (79 in Scheme 43) was synthesized by palladium-catalyzed N-aryl imination from 1,2-dibromobenzene and (S)-S-methyl-S-phenylsulfoximine with Pd2dba3 in 70% yield. 

From all these results, optically active sulfoximines, with their nitrogencoordinating site located at the close proximity to the stereogenic sulfur atom, have thus proven their efficiency as copper-ligands for asymmetric Diels-Alder and hetero Diels-Alder reactions. 

Werbitzky O, K Klier, H Felber H (1990) Asymmetric induction of four chiral cenbters by hetero Diels-Alder reaction of a chiral nitrosodienmophile. Liebigs Ann Chem 267-270. 

A new noncarbohydrate-based enantioselective approach to (—)-swainsonine was developed in which the key step was an aqueous intramolecular asymmetric hetero-Diels-Alder reaction of an acylni-troso diene (Eq. 12.57).128 Under aqueous conditions there was significant enhancement of the trans stereoselectivity relative to the reaction under conventional nonaqueous conditions. 

The presence of a small amount of water was found beneficial for several asymmetric hetero-Diels-Alder reactions. The asymmetric catalysis... 

The asymmetric synthesis of (4R,93, 9aR)-4-phenyl-l-trimethylsilyloxy-9-vinylperhydropyrido[2,T ][l,4]oxazine with a high level of stereoselectivity in the cyclization of (3R,5R)-5-phenyl-3-phenylsulfanyl-4-(6-trimethylsilanyl-hex-4-enyl)-2-trimethylsilyloxy-morpholine was rationalized via AMI calculations <1998T10309>. AMI calculations suggested that the formation of l,6-dioxo-l,3,4,6,7,8-hexahydropyrido[2,Tf][l,4]oxazine-9-carboxylates 230 from acroyl chlorides 228 and 1,4-oxazinone 229 is favored over the hetero-Diels-Alder condensation (Equation 45) <1996JOC5736>. 

A) in Scheme l).9 Furthermore, asymmetric Diels-Alder reactions have been developed in LPDE solutions or using hetero-bimetallic catalysts containing lithium ions (compound... 

Many examples of asymmetric reactions catalyzed by copper complexes with chiral ligand systems have been reported. In particular, various copper-bis(oxazoline) catalysts (e.g., complexes (H) to (L), Scheme 48) are effective for carbon-carbon bond-forming reactions such as aldol,204 Mukaiyama-Michael, Diels-Alder,206 hetero Diels-Alder,207,208 dipolar cycloaddition,209,210... 

The carbonyl group in a ketone or aldehyde is an extremely versatile vehicle for the introduction of functionality. Reaction can occur at the carbonyl carbon atom using the carbonyl group as an electrophile or through enolate formation upon removal of an acidic proton at the adjacent carbon atom. Although the carbonyl group is an integral part of the nucleophile, a carbonyl compound can also be considered as an enophile when involved in an asymmetric carbonyl-ene reaction or dienophile in an asymmetric hetero Diels-Alder reaction. These two types of reaction are discussed in the next three chapters. 

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