Asymmetric synthesis of a dopamine D1 agonist, dihydrexidine from d-serine

Malhotra, Rajesh; Ghosh, Amit; Ghosh, Rajib; Chakrabarti, Sagar; Dutta, Swarup; Dey, Tushar K.; Roy, Shibendu Shekhar; Basu, Sourav; Hajra, Saumen

doi:10.1016/j.tetasy.2011.08.014

Cited by 15 publications

(10 citation statements)

References 19 publications

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“…Reduction of 9 with sodium borohydride produced intermediate 10 as a mixture of two diastereomers (7:1 d.r.). Friedel–Crafts cyclization of 10 in trifluoroacetic acid (TFA) then provided tetrahydronaphthalene 11 in 87 % yield (5:1 d.r.)…”

Section: Methodsmentioning

confidence: 99%

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Wang

Zhu

2016

Angew Chem Int Ed

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Section: Methodsmentioning

confidence: 99%

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Wang

Zhu

2016

Angew Chem Int Ed

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“…These trans‐ aminotetralins could easily be obtained from 1‐aryl‐2‐nitrotetralins 4 . Consequently, the synthetic utility of this methodology was further demonstrated by the transformation of dihydro‐3‐nitronaphthalene 2d to (+)‐dihydrixdine,8c,d,11b–d a dopamine D1 agonist (Scheme ). To this end, 2d was reacted with PhB(OH) 2 3a in the presence of Rh(acac)(C 2 H 4 ) 2 ‐ L9 as a catalyst under optimized conditions.…”

Section: Methodsmentioning

confidence: 99%

“…Zn/HCl‐mediated reduction of the trans‐ 4da produced trans‐ 2‐amino‐1‐phenyltetralin and subsequent nosyl protection with NsCl and Et 3 N in DCM provided N ‐nosylaminotetralin 5 as a pale yellow solid with 61% yield over two steps. Recrystalization of the compound 5 from methanol at 0 °C crystallized out the minor enantiomer and enhanced the ee of the mother liquor to 98% with 72% recovery yield 8c,d. The optical rotation of 5 {[α]${{{25\hfill \atop {\rm D}\hfill}}}$ : −60 ( c 1.0, CHCl 3 )} matches very well with literature8c data {[α]${{{25\hfill \atop {\rm D}\hfill}}}$ : −64.2 ( c 1.0, CHCl 3 )}, thus confirming the absolute stereochemistry as 1 R ,2 R .…”

Section: Methodsmentioning

confidence: 99%

Rhodium‐Catalyzed Enantioselective Conjugate Addition of Arylboronic Acids to Dihydronitronaphthalenes

et al. 2012

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“…Therefore,t he formation of enantioenriched 2a did not occur by an on-stereoselective pinacol rearrangement to (AE)-2a followed by CPA-catalyzed enantioselective protonation of its enol form. Friedel-Crafts cyclization of 10 in trifluoroacetic acid (TFA) [25] then provided tetrahydronaphthalene 11 in 87 %yield (5:1 d.r.). Should the reaction proceed through an S N 2' mechanism, rearrangement via postulated transition state C (or D)s hould be competitive,l eading to product 2g.F urthermore,i ft he reaction indeed proceeded through an S N 2' mechanism, migration of the electron-rich aryl group (4-methoxyphenyl), which has ah igher migratory aptitude,v ia TS D would dominate,l eading to an isomer of 2g.H owever,t hese scenarios did not occur under our conditions.F inally,t he reaction of (Z)-2-butene-1,4-diol 1v under our standard conditions provided dihydrofuran 5 in 98 %yield, indicating that in this case,the ring closure is much faster than the double-bond isomerization via the allylic cation (Scheme 4b).…”

Section: Angewandte Chemiementioning

confidence: 99%

“…Reduction of 9 with sodium borohydride produced intermediate 10 as am ixture of two diastereomers (7:1 d.r.). Friedel-Crafts cyclization of 10 in trifluoroacetic acid (TFA) [25] then provided tetrahydronaphthalene 11 in 87 %yield (5:1 d.r.). [26] In conclusion, we have developed the first enantioselective vinylogous pinacol rearrangement of 1,4-diols catalyzed by achiral N-triflyl phosphoramide.The formation of achiral contact ion pair between the intermediary allylic cation and the conjugated base of the chiral Brønsted acid was proposed to be responsible for the observed enantioselectivity.T he utility of this transformation was illustrated by the subsequent conversion of the resulting b,g-unsaturated ketones into enantioenriched polysubstituted tetrahydrofuran and tetrahydronaphthalene derivatives.…”

Section: Angewandte Chemiementioning

confidence: 99%

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Wu,

Wang,

Zhu

2016

Angewandte Chemie

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An enantioselective pinacol rearrangement of functionalized (E)-2-butene-1,4-diols was developed. In the presence of a catalytic amount of a chiral BINOL-derived N-triflyl phosphoramide, these 1,4-diols rearranged to b,g-unsaturated ketones in excellent yields and enantioselectivities. The formation of a chiral ion pair between the intermediary allylic cation and the chiral phosphoramide anion was postulated to be responsible for the highly efficient chirality transfer. These chiral building blocks were further converted into enantioenriched polysubstituted tetrahydrofuran and tetrahydronaphthalene derivatives.Pinacol rearrangements, which convert 1,2-diols into ketones under acidic conditions, are a blueprint for a group of carbenium-based molecular reorganization processes.[1] As such reactions generate a new stereogenic center, the ability to control the stereochemical outcome would significantly expand their synthetic utility. However, several factors intrinsic to the reaction mechanism have made this endeavor highly demanding. First, the regioselective generation of one of the two possible carbenium intermediates under strongly acidic conditions is difficult. Second, differentiation of the prochiral faces of highly reactive planar carbocation intermediates is a formidable challenge as it falls out of the reach of typical Lewis acid and Brønsted acid catalysis. As a matter of fact, Antillas chiral phosphoric acid (CPA) catalyzed rearrangement of indolyl diols is the only example of an enantioselective pinacol rearrangement to date (Scheme 1 a).[2] In this transformation, the benzylic cation is generated regioselectively and stabilized in the form of conjugated iminium species A, [3] thereby facilitating the transfer of chiral information. Indeed, imines are the most widely exploited substrates in CPA-catalyzed asymmetric transformations. [4,5] To circumvent the aforementioned challenges, a number of efficient catalytic enantioselective semipinacol rearrangements have been developed. [6][7][8] Two key structural elements have been strategically incorporated into the substrates of these reactions in order to a) regioselectively generate the cationic intermediate or its equivalent and b) render the 1,2-CÀC bond shift a ring-strain-releasing process (Scheme 1 b). While the synthetic significance of these transformations is self-evident, constraints imposed on the substrate structure have nevertheless limited the full exploitation of the pinacol rearrangement. In connection with our ongoing studies of organocatalytic enantioselective transformations, [9] we became interested in the chiral contact ion pairs [10] formed between a CPA and cationic intermediates other than iminium species, [11,12] and we chose allylic cations [13] as our playground. We herein report a catalytic enantioselective vinylogous pinacol rearrangement of 1,4-diols 1 to b,gunsaturated ketones 2 (Scheme 1 c) and provide evidence that supports the hypothesis that chiral allylic contact ion pair B is a key intermediate for the transfer ...

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Asymmetric synthesis of a dopamine D1 agonist, dihydrexidine from d-serine

Cited by 15 publications

References 19 publications

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Rhodium‐Catalyzed Enantioselective Conjugate Addition of Arylboronic Acids to Dihydronitronaphthalenes

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

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