Stereochemistry of the Decomposition of N-Nitroso- and N-Amino-α,α'-dimethyldibenzylamine<sup>1</sup>

Overberger, C. G.; Marullo, N. P.; Hiskey, Richard G.

doi:10.1021/ja01467a028

Cited by 113 publications

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“…Amide 12 is readily accessible on a large scale in three steps from (R)-α-phenylethylamine [38] and shows a high enantioselectivity in deprotonation reactions [26] [27] [39] . Treatment of 12 in THF at low temperatures with ketone 9 and trapping of the lithium enolate 13 formed by reaction with ClSiMe 3 gave the enol ether 8a which had, however, only a low ee value (Table 1, entry 1).…”

Section: Resultsmentioning

confidence: 99%

“…Because of the ready hydrolysis of 8a on silica gel, which made its chromatographic purification on a preparative scale exceedingly difficult, the triethylsilyl ether 8b was prepared. Deprotonation of 9 was carried out with 12·LiCl, which was prepared directly by treatment of (R,R)-bis(phenylethyl)ammonium chloride [38] with 2 equivalents of nBuLi [40] [41] . Reaction of thus formed 13 with ClSiEt 3 gave 8b with an ee value of 92% in 95% yield (Table 1, entry 5).…”

Section: Resultsmentioning

confidence: 99%

“…MPLC (hexanes/EtOAc, 2:1) of the residue provided 29 (1.98 g, 63%) and 30 (0.99 g, 32%) as colorless oils. (38): A solution of 28 (69 mg, 0.55 mmol) in CH 2 Cl 2 (4 ml) was treated at room temp. with Et 2 O·BF 3 (78 mg, 0.55 mmol), and the resulting mixture was cooled immediately to Ϫ95°C.…”

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Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Vaulont

Gais²,

Reuter

et al. 1998

Eur. J. Org. Chem.

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Asymmetric total syntheses of 3‐oxacarbacyclin (4) and 3‐oxaisocarbacyclin (5) have been achieved by a new and common route. The key step of these syntheses is an enantioselective deprotonation of the prochiral ketone 25 with lithium (R,R)‐bis(phenylethyl)amide (12) in the presence of LiCl. Treatment of the thus formed enolate 26 with ClSiEt3 gave the enol ether 27 of 92% ee in 94% yield. Deprotonation of the analogous prochiral ketone 9 with 12 in the presence of LiCl followed by reaction of the enolate 13 with ClSiEt3 led to isolation of the silyl enol ether 8b of 92% ee in 95% yield. A study of the deprotonation of 9 with the chiral lithium amides 14−19 showed that 12 in combination with LiCl is the optimal base in terms of enantioselectivity and accessibility. The ω‐side chain in 4 and 5 was established by a Mukaiyama reaction of 27 with the unsaturated aldehyde 28, leading to ketone 39 of 90% de, in combination with a stereoselective Pd‐catalyzed allylic rearrangement of acetate 47 to the isomeric acetate 48 and a Mitsunobu reaction of the allylic alcohol 49. The key step in the construction of the α‐side chain in 4 is a Horner‐Wadsworth‐Emmons reaction of ketone 7c with the 8‐phenylnormenthol‐containing phosphonoacetate 56 which gave ester 60 of 90% de. Ester 60 was obtained diastereomerically pure by chromatography in 72% yield from 7c. Reduction of 60 furnished the allylic alcohol 62 which was converted to 4 in a standard fashion. It is at the stage of the α,β‐unsaturated ester 60 where divergence into synthesis of 5 was made. Selective isomerization of 60 to the β,γ‐unsaturated ester 66 of 97% ie in 91% yield was accomplished by deprotonation of 60 with 12 to enolate 65 and its subsequent regioselective protonation. By a similar reaction sequence the isomeric α,β‐unsaturated ester 61 was converted to the ß,γ‐unsaturated ester 69 of 97% ie in 88% yield. Reduction of 66 afforded the homoallylic alcohol 71 which was converted to 5 in a standard fashion.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Vaulont

Gais²,

Reuter

et al. 1998

Eur. J. Org. Chem.

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“…The most important methodologies developed to prepare ␣-chiral amines in enantiomerically pure form rely on either chemical resolution or on the use of readily available chiral synthons as building blocks. More recently, the development of efficient chiral auxiliaries has led to the extensive use of chiral imines as precursors to ␣-chiral amines by alkylation chemistry (5-9) or hydrogenation (10).…”

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confidence: 99%

Catalytic asymmetric addition of diorganozinc reagents to N -phosphinoylalkylimines

Côté

Boezio

Charette

2004

Proc. Natl. Acad. Sci. U.S.A.

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The synthesis of ␣-chiral amines bearing two alkyl groups has been hampered by the accessibility and stability of the alkylimine precursor. Herein, we report an efficient strategy to generate the alkyl-substituted imine in situ that is compatible with the MeDuPHOS monoxide⅐Cu(I) catalyzed addition of diorganozinc reagents. The sulfinic acid adduct of the imine is readily prepared by mixing diphenylphosphinic amide, the aldehyde, and sulfinic acid. The sulfinic acid adduct is generally isolated by filtration. The addition of diorganozinc reagents in the presence of Me-DuPHOS monoxide⅐Cu(I) and the in situ-generated imines affords the corresponding ␣-chiral amines in high yields and enantiomeric excesses.

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“…16 More recently, we described a thermal diastereoselective ␣-iminoamine rearrangement of a 2-benzyl-2-iminocyclohexanamine substrate. 17 Indeed, the treatment of rac-2-benzyloxycyclohexanone with two equivalents of either (+)-or (−)-phenylethylamine yielded a nonequimolar mixture of two diastereomeric (E)-imines 2 (ds 56%) with like induction at C-2.…”

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confidence: 99%

Expeditious synthesis and chromatographic resolution of (+)- and (?)-trans-1-benzylcyclohexan-1,2-diamine hydrochlorides

Bisel¹,

Schlauch²,

Weckert

et al. 2001

Chirality

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The hitherto unknown (-)- and (+)-1-benzylcyclohexan-1,2-diamine hydrochlorides 4a. HCl and 4b. HCl were synthesized by means of diastereoselective alpha-iminoamine rearrangement with subsequent imine reduction and hydrogenolysis. The relative trans-configuration as well as the absolute (1S,2R) and (1R,2S) configurations of 4a and 4b, respectively, were elucidated on the basis of an X-ray analysis of 3b. HCl. The enantiomeric excess (ee) values of the title compounds (>99%) were determined by chiral HPLC on a Chirex (D) Penicillamine column.

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Stereochemistry of the Decomposition of N-Nitroso- and N-Amino-α,α'-dimethyldibenzylamine¹

Cited by 113 publications

References 0 publications

Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Catalytic asymmetric addition of diorganozinc reagents to N -phosphinoylalkylimines

Expeditious synthesis and chromatographic resolution of (+)- and (?)-trans-1-benzylcyclohexan-1,2-diamine hydrochlorides

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Stereochemistry of the Decomposition of N-Nitroso- and N-Amino-α,α'-dimethyldibenzylamine1

Cited by 113 publications

References 0 publications

Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Asymmetric Synthesis of 3-Oxacarbacyclin and 3-Oxaisocarbacyclin by a Common Enantioselective Deprotonation Based Route

Catalytic asymmetric addition of diorganozinc reagents to N -phosphinoylalkylimines

Expeditious synthesis and chromatographic resolution of (+)- and (?)-trans-1-benzylcyclohexan-1,2-diamine hydrochlorides

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Stereochemistry of the Decomposition of N-Nitroso- and N-Amino-α,α'-dimethyldibenzylamine¹