Lewis Acid-Promoted Conjugate Addition of Dienol Silyl Ethers to Nitroalkenes:  Synthesis of 3-Substituted Azepanes

Denmark, Scott E.; Xie, Min

doi:10.1021/jo071126i

Cited by 41 publications

(19 citation statements)

References 23 publications

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Section: Resultssupporting

confidence: 92%

“…[Scheme 2, Equation (5)]. [7] To be mentioned also, is the elegant method described recently which affords highly electrophilic 2-methylene-1,3-dicarbonyl compounds E [Scheme 2, Equation (6)]. [8] The synthesis of the αunsaturated acylsilanes 3 has been performed by using slight optimizations (see Scheme 3 and In a next step, the MBH reaction was successfully extended to other acylsilanes (Scheme 5 and Table 2).…”

Section: Resultsmentioning

confidence: 99%

“…This result is in agreement with literature data indicating that conjugated acylsilanes are more easily cleaved under photolytic conditions that non conjugated substrates. [6] Similar reactions have been performed starting from the transposed (E) acylsilane 14′a. However, they did not afford the expected conju- gated aldehyde, and they gave only E-Z equilibration of this molecule, without hydrolysis of the acylsilane unit.…”

Section: Resultsmentioning

confidence: 99%

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α‐β Unsaturated Acylsilanes as Surrogates of Acrolein for Morita–Baylis–Hillman Reactions

et al. 2018

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α‐β‐unsaturated acylsilanes are excellent substrates for Morita–Baylis–Hillman (MBH) reactions, affording the expected adducts in good to excellent yields. In these derivatives, as well as the corresponding acetates, the acylsilanes can be smoothly transformed into aldehydes by irradiation at 365 nm in acetone or THF/water mixtures. Therefore α‐β unsaturated acylsilanes are very useful surrogates for acrolein in MBH reactions, allowing easy preparation of simple and highly functionalized new building blocks for synthetic applications.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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α‐β Unsaturated Acylsilanes as Surrogates of Acrolein for Morita–Baylis–Hillman Reactions

et al. 2018

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“…Since their discovery by Brook in 1957, 1-3 acylsilanes have been the one of the most powerful and efficient compounds that have the silicon directly attached to the carbonyl group, exhibiting particular physical and chemical properties, [4][5][6][7][8] so that they can be easily transformed into many different derivatives in one pot, such as acid, 9-12 ketone, [13][14][15] alcohol, 16,17 aldehyde, 11,18,19 cyanogen, 20 amide 12,20,21 and ester. 20,22 In addition to these radical reactions, a great deal of effort has been devoted to the development of various other kinds of acylsilane reactions, for instance, stereocontrolled nucleophilic additions, 23 stereocontrolled aldol reactions, 24 cyclization, 25 coupling reaction, 26 α-halogenations, 3 and enantioselective reduction.…”

Section: Introductionmentioning

confidence: 99%

Organocatalytic asymmetric Michael reaction with acylsilane donors

et al. 2013

Org. Biomol. Chem.

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We have developed an organocatalytic asymmetric Michael reaction of acylsilane through the selection of acylsilane substrates and organocatalysts, thus creating a rare example of acylsilane α-alkylation with a chiral guanidine catalyst, which afforded products in good yields and high stereoselectivity. The corresponding adducts described here have also been demonstrated to be useful in the synthesis of unnatural amino acids and biologically active compounds.

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“…Reduction of 16 with Zn/NH 4 Cl(aq) in EtOH [17] afforded an intermediate primary amine cleanly, which, to our surprise and in contrast to previously investigated systems, did not spontaneously condense to form the imine. [21] Treatment of the crude reaction mixture with Boc anhydride yielded 17 (85 %), and at this point the minor C(18) epimer arising from the conjugate addition could be separated by chromatography on silica gel. [20] Ozonolysis of 17, followed by reductive workup (PPh 3 ) and selective reduction (NaBH(OAc) 3 ) of the aldehyde afforded primary alcohol 18 (72 % over 2 steps).…”

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confidence: 99%

Total Synthesis of (+)‐Daphmanidin E

2011

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The daphniphyllum alkaloids have inspired organic chemists to devise novel strategies and to develop tailored methods aimed at synthesizing these complex structures. [1,2] The daphmanidins constitute a recent addition to this structurally diverse class of alkaloids isolated from Daphniphyllaceae. These can be further categorized into two skeletal types, namely type A (hexacyclic) and type C (pentacyclic).[1] The characteristic feature of the A-type alkaloids is an unprecedented hexacyclic structure, which includes a fused dihydropyrrole along with an embedded deca-or octahydrocyclopentazulene (oxide) around a central bicyclo[2.2.2]octane (Scheme 1).Herein, we describe the successful total synthesis of (+)-daphmanidin E, which is also the first synthesis of a type A daphmanidin alkaloid. The key features of the strategy involve rapid access to an enantiomerically pure bicyclo-[2.2.2]octadione and elaboration around its periphery through the implementation of two Claisen rearrangements, a diastereoselective hydroboration, and a cobalt-catalyzed alkylHeck cyclization.Daphmanidin E (1, Scheme 1) was isolated in 2006 from leaves of Daphniphyllum teijsmannii, and was shown to exhibit moderate vasorelaxant activity on rat aorta.[3] The complex architecture with three quaternary stereogenic centers and a central bicyclo[2.2.2]octane core constitutes a challenging target. We became attracted by the possibility of starting from the readily available building block 3, which features two quaternary stereogenic centers and the bicyclo-[2.2.2]octane skeleton with suitably functionalized bridgehead positions (Scheme 2). The C(1) ketone (daphmanidin numbering) provides a handle for the introduction of the quaternary center at C(8) through alkylation reactions or Claisen rearrangements, and one of the bridgehead carboxylate groups would provide entry to the fused dihydropyrrole. Key to the overall plan is a late-stage cyclization through an alkyl-Heck coupling to access the embedded seven-membered ring of the octahydroazulene (see 2, Scheme 2).The synthesis commenced with the C 2 -symmetric, enantiomerically enriched bicyclo[2.2.2]octadione (À)-3 (e.r. ! 95:5; Scheme 3). This compound was obtained by resolution Scheme 2. Retrosynthetic analysis of daphmanidin E (PG = protection group). Scheme 1. Type A daphmanidin alkaloids.Scheme 3. Reagents and conditions: a) 1,3-propanediol, pTsOH (10 mol %), PhH, reflux; then acetone, pTsOH (10 mol %), 50 8C, 88 %; b) KHMDS, 2-(NTf 2 )-pyridine, THF, À40 8C, 87 %; c) C 3 H 5 OSitBuPh 2 , 9-BBN, [Pd 2 (dba) 3 ]/CHCl 3 (2 mol %), AsPh 3 (16 mol %), K 3 PO 4 , DMF/ THF/H 2 O, 45 8C, 89 %; d) BH 3 ·SMe 2 , THF, RT, then NaBO 3 ·4H 2 O; DIBAL, THF, À25 8C, 72 %; e) pTsOH (5 mol %), acetone, 50 8C; BzCl, pyridine, DMAP (cat.), CH 2 Cl 2 , RT, 95 % over 2 steps. pTsOH = ptoluenesulfonic acid, KHMDS = potassium hexamethyl disilazide, 9-BBN = 9-borabicyclo[3.3.1]nonane, dba = dibenzylideneacetone, Bz = benzoyl, DIBAL = iBu 2 AlH, DMAP = 4-dimethylaminopyridine; Tf = trifluoromethylsulfonyl, TBDPS = te...

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Lewis Acid-Promoted Conjugate Addition of Dienol Silyl Ethers to Nitroalkenes: Synthesis of 3-Substituted Azepanes

Cited by 41 publications

References 23 publications

α‐β Unsaturated Acylsilanes as Surrogates of Acrolein for Morita–Baylis–Hillman Reactions

α‐β Unsaturated Acylsilanes as Surrogates of Acrolein for Morita–Baylis–Hillman Reactions

Organocatalytic asymmetric Michael reaction with acylsilane donors

Total Synthesis of (+)‐Daphmanidin E

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