Studies on enolate chemistry of 8-thiabicyclo[3.2.1]- octan-3-one: enantioselective deprotonation and synthesis of sulfur analogs of tropane alkaloids

2001 ◽  
Vol 79 (11) ◽  
pp. 1792-1798 ◽  
Author(s):  
Marek Majewski ◽  
Marc DeCaire ◽  
Pawel Nowak ◽  
Fan Wang
Keyword(s):  
Acetic Anhydride ◽  
Key Words ◽  
Carboxylic Acids ◽  
Alkylating Agents ◽  
Tropane Alkaloids ◽  
Lithium Amides ◽  
Lithium Enolate ◽  
Unsaturated Carboxylic Acids ◽  
Derivatives Of ◽  
Enantioselective Deprotonation

Enantioselective deprotonation of 8-thiabicyclo[3.2.1]octan-3-one (1) with chiral lithium amides, followed by reactions with electrophiles affords sulfur analogs of tropane alkaloids of pyranotropane family. Thus, deprotonation of 1 with (S)-N-(diphenyl)methyl-1-phenylethylamine (11d), followed by the reaction of the resulting nonracemic enolate with benzaldehyde gives the corresponding aldol product as one diastereoisomer (exo, threo) and in high enanatiomeric purity (95% ee). Trimethylsilyl chloride, acetic anhydride, and acyl cyanides react readily with the lithium enolate to give the corresponding derivatives of 1, however common alkylating agents fail to provide C-alkylated products. The reaction with acyl cyanides derived from α,β-unsaturated carboxylic acids (e.g., cinnamoyl cyanide) can be utilized in synthesis of thia-analogs of tropane alkaloids physoperuvine and isobellendine (13, 15).Key words: enantioselective deprotonation, tropane alkaloids.

Thiohydantoins. II. Thiohydantoins Derived from Aspartic and Glutamic Acids

1952 ◽  
Vol 5 (4) ◽  
pp. 721
Author(s):  
JM Swan
Keyword(s):  
Acetic Anhydride ◽  
Carboxylic Acids ◽  
Ammonium Thiocyanate ◽  
Derivatives Of ◽  
Isomeric Pairs ◽  
Acyl Derivatives

N-Acyl derivatives of the &carboxylic acids, aspartic and glutamic acids, yield the corresponding anhydrides when heated with acetic anhydride in the presence or absence of ammonium thiocyanate. In general these anhydrides form isomeric pairs of amides and anilides, and only one of each pair can be converted into the corresponding 2-thiohydantoin. The anhydrides from N-phenylacetyl- and N-p-nitro-benzoylglutamic acids, and N-acetylaspartic acid have been regarded hitherto as oxazolones.

Enantioselective ring opening of tropinone. A new entry into tropane alkaloids

1997 ◽  
Vol 75 (6) ◽  
pp. 754-761 ◽  
Author(s):  
Marek Majewski ◽  
Ryszard Lazny ◽  
Agnieszka Ulaczyk
Keyword(s):  
Ring Opening ◽  
Stereoselective Synthesis ◽  
Tropane Alkaloids ◽  
Amine Hydrochloride ◽  
Lithium Amides ◽  
Ring Opening Reaction ◽  
Alkyl Chloroformates ◽  
Optically Pure ◽  
Enantioselective Deprotonation

The lithium enolate of tropinone reacts with alkyl chloroformates to give 6-N-carboalkoxy-N-methyl-2-cycloheptenones (4). These compounds can be produced enantioselectively, in up to 95% ee, if chiral lithium amides (derived from optically pure amines 5–7) are used for deprotonation of tropinone in the presence of additives. The effect of additives such as LiCl, LiBr, LiF, LiClO4, CeCl3, ZnCl2, LiOH, TMEDA, HMPA, and DMPU on enantioselectivity of this deprotonation–ring opening sequence varies from slight to very large depending on the chiral amide – additive combination. Especially large increases in enantioselectivity are observed when the chiral, C2 symmetrical, lithium bis-α,α′-methylbenzylamide (Li-5a) is used with one equivalent of LiCl. This reagent is best generated in situ from the corresponding amine hydrochloride and n-BuLi (2 equiv.). The ring-opening reaction combined with transposition of the carbonyl group (via Wharton reaction or allylic oxidation) provides a new method of stereoselective synthesis of tropane alkaloids having a protected hydroxyl at C-6 or C-7 (6β- and 7β-acetoxytropanes 14a, b) and physoperuvine (19). Keywords: enantioselective deprotonation, tropane alkaloids.

Unsaturated carboxylic acids in the one-pot synthesis of novel derivatives of 3,4-dihydro-2H-thiopyran

2021 ◽  
Author(s):  
Ekaterina А. Merkulova ◽  
Aleksei V. Kolobov ◽  
Konstantin L. Ovchinnikov ◽  
Victor N. Khrustalev ◽  
Valentine G. Nenajdenko
Keyword(s):  
Carboxylic Acids ◽  
One Pot ◽  
One Pot Synthesis ◽  
Unsaturated Carboxylic Acids ◽  
The One ◽  
Derivatives Of

The first reagent-controlled asymmetric halolactonizations. Dihydroquinidine-halogen complexes as chiral sources of positive halogen ion

1998 ◽  
Vol 76 (9) ◽  
pp. 1233-1237 ◽  
Author(s):  
Robert B Grossman ◽  
Robert J Trupp
Keyword(s):  
Key Words ◽  
Carboxylic Acids ◽  
Factors Affecting ◽  
Unsaturated Carboxylic Acids

The first reagent-controlled asymmetric halolactonizations are described. Complexes of I+ with O-acyl- and O-aryldihydroquinidines are used to promote the asymmetric halolactonization of prochiral θ, δ-unsaturated carboxylic acids with low but measurable and reproducible enantioselectivity. Experimental factors affecting the ee's are described. Key words: halocyclization, halogenation, halonium ions, chiral, stereoselective.

Enantioselective deprotonation of protected 4-hydroxycyclohexanones

1994 ◽  
Vol 72 (7) ◽  
pp. 1699-1704 ◽  
Author(s):  
Marek Majewski ◽  
John MacKinnon
Keyword(s):  
Hydroxy Group ◽  
Silyl Ether ◽  
Lithium Amides ◽  
Enol Acetates ◽  
Optically Pure ◽  
Derivatives Of ◽  
Enantioselective Deprotonation

A series of derivatives of 4-hydroxycyclohexanone (1a–g) with the hydroxy group protected as a silyl ether (1a, b), ether (1d, g), an acetal (1c), or an ester (1e, f) were deprotonated with chiral, optically pure, lithium amides 3–9. The resulting non-racemic enolates were trapped as enol acetates. The enantioselectivity of deprotonation was up to 74% ee.

Sign in / Sign up

Export Citation Format

Share Document