Sulfinimines Research Articles

ChemInform Abstract: Diastereoselective Coupling of N‐(tert‐Butyl)sulfinyl Imines and Dimethyl Malonate. Synthesis of Enantiomerically Enriched β‐Amino Esters and β‐Lactams.

AbstractHigher yields of the target compounds (III) are obtained in the presence of NaI compared to NaHCO3.

Stereoselective Synthesis of Carbohydrate-Derived N-Sulfonyl Aziridines

A novel reaction of iodomethyllithium with a variety of sugar-derived N-sulfinyl imines, under very mild conditions, is ­described. N-Sulfonyl aziridines were easily obtained in high yields and in moderate to good stereoselectivities through an addition/­oxidation protocol. A mechanism is proposed that is ­supported by the results of X-ray diffraction studies.

Stereoselective Addition of 2-Phenyloxazol-4-yl Trifluoromethanesulfonate to N-Sulfinyl Imines: Application to the Synthesis of the HCV Protease Inhibitor Boceprevir

The stereoselective addition of 2-phenyloxazol-4-yl trifluoromethanesulfonate to N-sulfinylimines is described. Vinyl anions derived from enol triflate 2 undergo 1,2-addition with a variety of aldimines to afford the corresponding secondary sulfonamides as single diastereomers. The absolute stereochemistry was confirmed by X-ray crystallography which provides support that the reaction proceeds through an open, nonchelate transition state. This methodology has been applied to the synthesis of the ketoamide fragment of the protease inhibitor boceprevir.

The stereoselective total synthesis of (−)-dihydrotetrabenazine

A highly stereoselective synthesis of (−)-dihydrotetrabenazine has been accomplished using (R)-tert-butanesulfinamide as a chiral source. The synthesis involves the allylation of chiral N-sulfinyl imine followed by ring closure of the resulting secondary amide with a tethered halide and the Evans-Aldol reaction as key steps.

Diastereoselective Coupling of N‐(tert‐Butyl)sulfinyl Imines and Dimethyl Malonate. Synthesis of Enantiomerically Enriched β‐Amino Esters and β‐Lactams

AbstractA diastereoselective coupling of dimethyl malonate with N‐(tert‐butyl)sulfinyl imines under solvent‐free conditions was developed, using NaHCO3 or NaI as base promoters. The resulting dimethyl 2‐(1‐aminoalkyl)malonates could be easily transformed successively to β‐amino esters and the corresponding β‐lactams with high optical purity.

ChemInform Abstract: Synthesis and Applications of Masked Oxo‐Sulfinamides in Asymmetric Synthesis

AbstractReview: ca. 50 refs.

Asymmetric Addition of Alkoxy Ethynyl Anion to Chiral N-Sulfinyl Imines

The addition of lithiated ynol ethers to chiral N-sulfinyl imines proceeds in high yield and diastereoselectivity. The selectivity is completely reversed by the addition of boron trifluoride. These alkoxypropargyl sulfinamides can be reduced to afford enol ethers, selectively oxidized to busyl derivatives, or the ynol ether can be hydrolyzed to afford β-amino esters.

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

Asymmetric Total Synthesis of (+)‐Merobatzelladine B

Synthesis and applications of masked oxo-sulfinamides in asymmetric synthesis

This short perspective reports on the synthesis and applications of a class of chiral amino carbonyl compounds, masked oxo-sulfinamides where the amine is protected with an N-sulfinyl moiety and the carbonyl group is protected as the ketal or 1,3-dithiane. These polyfunctionalized chiral building blocks are prepared by addition of organometallic reagents to masked oxo-sulfinimines (N-sulfinyl imines) or the addition of oxo-organometallic reagents and lithio-1,3-dithianes to sulfinimines. Because unmasking of the amino and carbonyl groups results in cyclic imines, these chiral building blocks are particularly useful for the asymmetric synthesis of functionalized nitrogen heterocycles, including prolines, pipecolic acids, pyrrolidines, homotropinones, tropinones, and tropane alkaloids such as cocaine and C-1 cocaine analogues.

Stable synthetic equivalents of N-unsubstituted imines: Part 1. Synthesis

The key role of imines in organic synthesis, for example in the synthesis of amine derivatives and nitrogen heterocycles, is well known. However, the instability of N-unsubstituted imines is often an obstacle to the selection of synthesis strategy. Therefore, it is rather topical to design stable imines with a readily removable group at the nitrogen atom. The first part of this review deals with the methods of synthesis of N-sulfinyl imines (including chiral), N-sulfonyl imines, N-phosphinoyl imines, N-acylimines, N-silylimines, N-(hexopyranosyl)imines, N-benzylimines, N-(methoxyphenyl)imines, N-allylimines, 1,3,5-trisubstituted 2,4-diazapenta-1,4-dienes, and N-(1-hydroxyethyl-2,2,2-trichloro)imines and the methods for removing these protective groups.

Design, Synthesis, and Biological Evaluation of Novel Fluorinated Ethanolamines

The preparation of novel fluorinated allylamines and their use as key fragments for the stereoselective synthesis of hydroxyethyl secondary amine (HEA)-type peptidomimetics is described. Our strategy employs chiral sulfinyl imines as synthesis intermediates, by treatment of hemiaminal precursors with two equivalents of vinylmagnesium bromide. The subsequent oxidation of the allylic amines to the corresponding epoxides was achieved by treatment with methyl(trifluoromethyl)dioxirane. Finally, epoxide ring opening with a range of nitrogen nucleophiles provided a library of HEA-derived peptidomimetics with a phenyldifluoromethylene moiety. The biological evaluation of these derivatives revealed compounds with remarkable BACE1 inhibitory activity. Docking studies revealed the influence of the fluorine atoms in the binding mode of the synthesized ligands. Furthermore, the biological evaluation of our final products and synthesis intermediates led to the discovery of compounds with antimicrobial activity against Mycobacterium and Nocardia species.

Relative stabilities of transition states determine diastereocontrol in sulfur ylide additions onto chiral N‐sulfinyl imines

Additions of methylphenylsulfonium methylide onto chiral non-racemic N-sulfinyl imines (R'-SO-N=CH-R, R'=t-butyl, R=protected diol), followed by ring closure, yield terminal aziridines with high diastereoselectivity. Control reactions have established that both N- and C- iminyl substituents impact product preference, and when properly matched, one addition product is selected almost exclusively. Using solution-phase density functional computational methods, minima and transition state searches have been performed to reveal the structural origins of the diastereoselectivity. Our computational findings indicate that ring closure is fast and irreversible, and consequently, the relative energies of the transition states for the competing Re/Si addition steps determine the product diastereomeric ratios. Analysis of addition transition state structures reveals the causes of selectivity as arising from the N- and C- iminyl substituents, and we identify the S (R) configuration of the N-sulfinyl sulfur atom as the dominant director of Si (Re) addition. The control attributed to the sulfur configuration is tied to an important favorable internal interaction between the sulfinyl oxygen and the iminyl hydrogen. The protected diol acts as a secondary director, owing to steric/electrostatic interactions with the approaching ylide.

ChemInform Abstract: One‐Pot Synthesis of Chiral α‐Methylene‐γ‐lactams with Excellent Diastereoselectivities and Enantioselectivities.

AbstractThe Zn‐promoted aza‐Barbier‐type allylation of sulfinyl imines with allyl bromides affords substituted α‐methylene γ‐lactams.

N-Sulfinyl Imines

N-Sulfinyl imines (sulfinimines) play an important role in asymmetric reactions. They display unique reactivity and stereoselectivity in the synthesis of amino group containing natural products and bioactive compounds. Furthermore, a wide variety of sulfinimines is efficiently prepared for many types of asymmetric reactions, and the chiral sulfinyl in the resultant product is easily removed under comparatively mild conditions. [¹]

Benzoquinone-derived sulfinyl imines as versatile intermediates for alkaloid synthesis: Total synthesis of (–)-3-demethoxyerythratidinone

The preparation and synthetic applications of benzoquinone monoketal-derived N-tert-butanesulfinyl imines is described. These synthetically versatile intermediates undergo highly diastereoselective 1,2-addition reactions with organometallic reagents to provide 4-aminocyclohexadienones in good yields. The utility of this methodology is demonstrated in a six-step enantioselective synthesis of (–)-3-demethoxyerythratidinone.

(2S)-2-[(2S*,5R*,6R*)-5,6-Dimethoxy-5,6-dimethyl-1,4-dioxan-2-yl]-1-[(S)-1,1-dimethylethylsulfonyl]aziridine

The reaction of a sulfur ylide with a chiral non-racemic sulfinyl imine afforded the desired aziridine in excellent yield and subsequent oxidation of the sulfinyl moiety dissolved in anhydrous dichloro­methane using a 75% aqueous solution of 3-chloro­per­oxy­benzoic acid afforded the title compound, C14H27NO6S. The configuration of the newly formed stereogenic center at the point of attachment of the 1,4-dioxane ring to the aziridine ring is S. The configurations of the pre-existing sites 2-, 5-, and 6-positions of the 1,4-dioxane ring prior to reaction of sulfinyl imine with the sulfur ylide are S, R, and R, respectively. The C—N bond lengths of the aziridine are 1.478 (2) and 1.486 (2) Å.

Total Syntheses of the Thiopeptides Amythiamicin C and D

The thiopeptides amythiamicin C and D were synthesized by employing amide bond formation, a Stille cross-coupling reaction, and two Negishi cross-coupling reactions as key transformations. The central 2,3,6-trisubstituted pyridine ring of the target compounds was introduced as a 2,6-dibromo-3-iodopyridine, which was selectively metalated at the 3-position and connected to the complete Southern fragment of the amythiamicins by a Negishi cross-coupling. For the synthesis of amythiamicin C, this step was followed by a Negishi cross-coupling at C-6 of the pyridine core. Subsequent attachment of the Eastern fragment was achieved by amide bond formation and macrolactam ring closure by a Stille cross-coupling at C-2. The Eastern bithiazole fragment of the amythiamins was constructed also by regioselective metalation and cross-coupling reactions. The pivotal step involved the diastereoselective addition of 4-bromothiazole-2-magnesium bromide to a chiral sulfinyl imine. For the synthesis of amythiamicin D, the order of cross-coupling at C-6, amide bond formation, and cross-coupling at C-2 was changed. The amide bond formation to the Eastern fragment was performed first and it was subsequently attempted to close the macrolactam by an intramolecular regioselective Stille cross-coupling at C-2. Despite the low regioselectivity of this reaction it paved the way to the immediate completion of the amythiamicin D synthesis when followed by a Negishi cross-coupling at C-6 with 2-zincated methyl thiazole-5-carboxylate.

A modular, efficient, and stereoselective synthesis of substituted piperidin-4-ols.

A modular, efficient, and stereoselective synthesis of substituted piperidin-4-ols.

Domino Imino-Aldol−Aza-Michael Reaction: One-Pot Diastereo- and Enantioselective Synthesis of Piperidines

Addition of α-arylmethylidene- or α-alkylidene-β-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to substituted piperidines is reported. Enantiopure piperidines are synthesized from chiral sulfinyl imines. Formation and the observed stereoselectivity of the products have been rationalized by mechanistic and computational studies.

Diastereoselective addition of lithium enolate of γ-substituted α-diazoacetoacetate to N-sulfinyl imines

Highly diastereoselective addition of lithium enolate of γ-substituted α-diazoacetoacetate to chiral N-sulfinyl imines has been developed. The addition products were further subjected to photo-induced Wolff rearrangement or Rh(II)-catalyzed intramolecular N-H insertion to afford chiral 4,5-disubstituted 2-oxo and 3-oxo pyrrolidines, respectively.