Catechol boron halides: mild and selective reagents for cleavage of common protecting groups

Boeckman, Robert K.; Potenza, Joan C.

doi:10.1016/s0040-4039(00)99058-0

Cited by 137 publications

(71 citation statements)

References 6 publications

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“…Trimethylsilyl halides such as Me,SiBr [33] produced some deprotected product, along with an equal amount of isomerized starting material. The only reagent which effected deprotection without any appreciable isomerization was B-bromocatecholborane [34]. The yields of alcohols 83 and 84 were generally between 60 and 70%, with the remainder of the mass balance being decomposition products (rather than isomerized compound).…”

Section: Scheme 1 1 Extension Of the Linearly Conjugated N-chromophomentioning

confidence: 99%

“…The solid was dissolved in a minimum amount of CH,Cl,, then hexane was added to precipitate the remaining phosphine oxide which was removed by filtration. Recrystallization from MeOH/CH,C12 yielded 57 (34 3 mmol) in dry T H F (400 nil) was added slowly a s o h of LDA in T H F (14.9 ml, 7.8 minol; prepared by the addition of 1 . 6~ BuLi in hexane (4.9 i d ) to a soh.…”

Section: -mentioning

confidence: 99%

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Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

Anthony¹,

Boldi²,

Rubin

et al. 1995

Helvetica Chimica Acta

125

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~ ~~The preparation of tetraethynylethene (3,4-diethynylhex-3-ene-1,j-diyne) 1 as well as of a great diversity of differentially mono-, di-, and triprotected derivatives by newly developed synthetic routes is described. These fully cross-conjugated molecules are versatile building blocks and precursors to two-dimensional all-C networks and novel C-rich nanoarchitecture with unusual structural and electronic properties, such as perethynylated expanded radialenes, or molecular wires and polymers with the novel polytriacetylene backbone. A key step in all of these routes was the Corey-Fuchs dihromoolefination of aldehydes and ketones. Dibromoolefination of silyl-protected penta-1,4-diyn-3-ones yielded the corresponding dibromomethylidene derivatives which, by twofold Pd-catalyzed alkyne coupling, were transformed into tetraethynylethene derivatives. In routes to tetraethynylethenes with free cis-or trans-enediyne moieties, dibromoolefination of aldehyde groups produced geminal dibromoethenes which, upon elimination/metallation with LDA followed by quenching with H+ or other electrophiles, yielded free or substituted ethynyl groups in high yields. Tetra-and triprotected tetraethynylethenes are rather stable compounds that could be isolated in pure form, whereas derivatives with two or more free -C-H termini were only stable in dilute solution and polymerized rapidly in pure form. A trans-bis-deprotected, trans-bis(triisopropylsily1)-protected derivative represented an exception and could be isolated as stable crystals. X-Ray analysis revealed that the two bulky (i-Pr)$i groups isolate the reactive chromophores from one another in the crystal and prevent intermolecular reactions. The structures of several tetraethynylethenes were revealed in high-quality X-ray crystal structures.

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Section: Scheme 1 1 Extension Of the Linearly Conjugated N-chromophomentioning

confidence: 99%

Section: -mentioning

confidence: 99%

Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

Anthony¹,

Boldi²,

Rubin

et al. 1995

Helvetica Chimica Acta

125

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“…Then, mild non-transition-metal-assisted deprotections ystems of the most usual PGs of amines (trityl, [11,12] Z, [13][14][15] Boc [14,[16][17][18] )o rcarboxylic acids [19] (tert-butyl, [18,[20][21][22][23] benzyl [24][25][26][27][28] esters) were reported,b esides al ow effectivem ethod for allyl ester, [27] and none for the alloc PGs. [29] Here, we reasoned that Lewis acids in aproticm edium needed to be explored in am ore systematic way for their chemoselective potential, amino-acids being indeeda ni deal model of functional group diversity and for racemizations tudies.D uring our campaign to find selectivec onditions to cleave ethyl esters while preserving the Fmoc group, we discovered the impressivep otentialo f MgI 2 ,e nlarginga fterwards the scopet of acile chemoselective cleavages of various standardsP Gs or PS-resins( Figure 1).…”

mentioning

confidence: 99%

MgI₂‐Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies

Berthet

Davanier

Dujardin

et al. 2015

Chemistry A European J

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“…Anhydrous TFA in CH 2 Cl 2 was not an option, as decomposition of the delicate trienoate linkage proved competitive. Turning to Lewis acids, B -bromocatecholborane 102 removed both the MOM and acetonide groups in (+)- 108 , but removal of the t -butyl group of the ester remained sluggish (Scheme 45C and D). …”

Section: Resultsmentioning

confidence: 99%

(+)-Sorangicin A: evolution of a viable synthetic strategy

et al. 2011

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An effective, asymmetric total synthesis of the antibiotic (+)-sorangicin A (1) has been achieved. Central to this venture was the development of first and second generation syntheses of the signature dioxabicyclo[3.2.1]octane core, the first featuring chemo- and stereoselective epoxide ring openings facilitated by a Co2(CO)6-alkyne complex, the second involving a KHMDS-promoted epoxide ring formation/opening cascade. Additional highlights include effective construction of the dihydro- and tetrahydropyran ring systems, respectively via a stereoselective conjugate addition/α-oxygenation protocol and a thioketalization/hydrostannane reduction sequence. Late-stage achievements entailed two Julia–Kociénski olefinations to unite three advanced fragments with high E-stereoselectivity, followed by a modified Stille protocol to introduce the Z,Z,E trienoate moiety, thereby completing the carbon skeleton. Mukaiyama macrolactonization, followed by carefully orchestrated Lewis and protic acid-promoted deprotections that suppressed isomerization and/or destruction of the sensitive (Z,Z,E)-trienoate linkage completed the first, and to date only, total synthesis of (+)-sorangicin A (1)

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Catechol boron halides: mild and selective reagents for cleavage of common protecting groups

Cited by 137 publications

References 6 publications

Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

MgI₂‐Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies

(+)-Sorangicin A: evolution of a viable synthetic strategy

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Catechol boron halides: mild and selective reagents for cleavage of common protecting groups

Cited by 137 publications

References 6 publications

Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials

MgI2‐Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies

(+)-Sorangicin A: evolution of a viable synthetic strategy

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MgI₂‐Mediated Chemoselective Cleavage of Protecting Groups: An Alternative to Conventional Deprotection Methodologies