Torsional Control of Epoxidation Stereoselectivity in 1,2-Dihydronaphthalenes. Transition State Modeling with Semiempirical Quantum Mechanics

Lucero, Melissa J.; Houk, K. N.

doi:10.1021/jo980760g

Cited by 38 publications

(40 citation statements)

References 11 publications

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“…The electrophilic anti-addition of HTIB to the double bond would lead to 12a, through the cyclic organoiodine intermediate 11. The approach of the electrophile occurs opposite to the remote methyl group, [27][28][29] explaining the stereoselectivity of this ring contraction, as well as of the other reactions discussed below. The adduct 12a would equilibrate to its more stable conformational isomer 12b, on which the required anti-periplanarity for the rearrangement is achieved.…”

Section: Mechanism Discussionmentioning

confidence: 99%

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes

Siqueira¹,

Ishikawa²,

Fogaça³

et al. 2011

J. Braz. Chem. Soc.

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Um protocolo livre de metais foi desenvolvido para sintetizar indanos através da contração de anel de 1,2-di-hidronaftalenos promovida por PhI(OH)OTs (HTIB ou reagente de Koser). Este rearranjo oxidativo pode ser realizado em diversos solventes (MeOH, CH 3 CN, 2,2,2-trifluoroetanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), e uma mistura 1:4 de TFE:CH 2 Cl 2 ) em condições brandas. A contração de anel fornece indanos trans-1,3-dissubstituídos diastereosseletivamente, os quais são difíceis de obter em química orgânica sintética.A metal-free protocol was developed to synthesize indanes by ring contraction of 1,2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser's reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH 3 CN, 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH 2 Cl 2 ) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1,3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry.Keywords: indanes, hypervalent iodine, ring contraction, 1,2-dihydronaphthalenes, rearrangements IntroductionThe indane ring system is present in several natural products and in non-natural compounds with remarkable biological activity.1 Consequently, efforts have continuously been made to develop new routes to obtain molecules with this unit.2 A typical strategy to synthesize a functionalized indane is by selecting an appropriate indanone, which is then elaborated into the target molecule. 2,3 As tetralones are usually cheaper than indanones, the preparation of indanes starting from a tetralone (or a derivative) through a ring contraction rearrangement could be advantageous. 4 In the last years, hypervalent iodine reagents have become an essential tool in synthetic organic chemistry due to the plethora of reactions that can be performed with them in excellent yield and selectivities. 5 Moreover, hypervalent iodine compounds represent in many cases an alternative to toxic heavy metals. 5 Although the oxidative rearrangement of alkenes mediated by iodine(III) has been described in some papers, 6 the ring contraction of 1,2-dihydronaphthalenes was reported for a few substrates using only p-Me-C 6 H 4 -IF 2 , 6 which led to fluorinated indanes.Herein, we describe an efficient metal-free protocol for the synthesis of indanes under mild conditions. In a preliminary communication, we report the ring contraction of 1,2-dihydronaphthalenes (which are obtained from 1-tetralones) mediated by PhI(OH)OTs (HTIB or Koser's reagent) for a few substrates. 7 In this article, the oxidation of several additional substrates is presented, better defining the reaction scope. Additionally, other reaction conditions were Metal-Free Synthesis of Indanes by Iodine(III)-Mediated Ring Contraction J. Braz. Chem. Soc. 1796 discovered using fluoroalcohols as solvent, which highly improved isolated yields. The best condition employed a 4:1 mixture of CH 2 Cl 2 -TFE that led to indanes in...

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Section: Mechanism Discussionmentioning

confidence: 99%

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes

Siqueira¹,

Ishikawa²,

Fogaça³

et al. 2011

J. Braz. Chem. Soc.

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“…43 Figure 21 shows the PM3 optimized diastereomeric transition structures for the epoxidations of three different substrates; single point energy calculations were performed using RHF/6-21G*. For compound 14 , the α–attack TS14α is calculated to be more stable than the β–attack TS14β by 2.1 kcal/mol.…”

Section: Stereoselectivities Of Reactions Of 5- 6- and 7-membered Cmentioning

confidence: 99%

Torsional control of stereoselectivities in electrophilic additions and cycloadditions to alkenes

Wang

Houk

2014

Chem. Sci.

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“…24 Assuming for steric reasons that C-O bond formation is more advanced at alkene carbon b, torsional effects would favor epoxidation from the alkene stereoface anti to the indoline bridge, as depicted in Figure 3. 25 Without success, we explored initially the possibility of converting tetracyclic epoxide 34 to allylic alcohol 36 using lithium amide bases at various temperatures (Scheme 6). 26 For example, reaction of epoxide 34 with lithium diethylamide in THF at −40 °C led to rapid loss of the methyl carbamate group.…”

Section: Attempts To Construct the Minfiensine Ring System By An Intrmentioning

confidence: 99%

Total Synthesis of the Strychnos Alkaloid (+)-Minfiensine: Tandem Enantioselective Intramolecular Heck−Iminium Ion Cyclization

et al. 2008

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A 1,2,3,4-tetrahydro-9a,4a-(iminoethano)-9H-carbazole (4) is a central structural feature of the Strychnos alkaloid minfiensine (1) and akuammiline alkaloids such as vincorine (5) and echitamine (6). A cascade catalytic asymmetric Heck-iminium cyclization was developed that rapidly provides 3,4-dihydro-9a,4a-(iminoethano)-9H-carbazoles in high enantiomeric purity. Two sequences were developed for advancing 3,4-dihydro-9a,4a-(iminoethano)-9H-carbazole 27 to (+)-minfiensine. In our first-generation approach, a reductive Heck cyclization was employed to form the fifth ring of (+)-minfiensine. In a second more concise total synthesis, an intramolecular palladium-catalyzed ketone enolate vinyl iodide coupling was employed to construct the final ring of (+)-minfiensine. This second-generation total synthesis of enantiopure (+)-minfiensine was accomplished in 6.5% overall yield and 15 steps from 1,2-cyclohexanedione and anisidine 13. A distinctive feature of this sequence is the use of palladium-catalyzed reactions to form all carboncarbon bonds in the transformation of these simple precursors to (+)-minfiensine.

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Torsional Control of Epoxidation Stereoselectivity in 1,2-Dihydronaphthalenes. Transition State Modeling with Semiempirical Quantum Mechanics

Cited by 38 publications

References 11 publications

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes

Metal-free synthesis of indanes by iodine(III)-mediated ring contraction of 1, 2-dihydronaphthalenes

Torsional control of stereoselectivities in electrophilic additions and cycloadditions to alkenes

Total Synthesis of the Strychnos Alkaloid (+)-Minfiensine: Tandem Enantioselective Intramolecular Heck−Iminium Ion Cyclization

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