Ortho lithiation of monosubstituted benzenes: a quantitative determination of pKa values in tetrahydrofuran

Fraser, Robert R.; Bresse, Monique; Mansour, Tarek S.

doi:10.1021/ja00364a078

Cited by 71 publications

(45 citation statements)

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“…L'evidence de I'infrarouge et de la rmn de "N n'est pas claire a cause du manque de modtles appropries. pK, du produit 1 est environ de 2 unites (100 fois) plus acide que celui du benzonitrile (6). Ces resultats suggkrent une aciditt plus importante pour les protons benzyliques que pour le proton aromatique de la position 2.…”

Section: -10unclassified

Le lithio-2 naphtalène carbonitrile-1 et ses produits de substitutions

Fraser¹,

Savard²

1986

Can. J. Chem.

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Lithiation of 1-naphthonitrile provides the 2-lithio derivative exclusively. Reaction of this intermediate with ten different electrophiles produces 2-substituted derivatives in moderate to good yields. 2-Alkyl-1-naphthonitriles are readily lithiated and further alkylated to provide alkyl substituents modified at the α position. The pKa values for the hydrogen at the 2-position of 1-cyanonaphthalene and 2-methyl-1-cyanonaphthalene have been determined to be 36.3 and 28.5, respectively.

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Section: -10unclassified

Le lithio-2 naphtalène carbonitrile-1 et ses produits de substitutions

Fraser¹,

Savard²

1986

Can. J. Chem.

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“…The NH acidity of the phenylogous sulfinamide 45 should be significantly higher than its CH ortho acidity. [34,35] The aryllithium derivative 46 would thus not be stable under the reaction conditions but would undergo transmetalation to the lithium salt 47. . [9] It was found that the lithiation of the sulfone 51 with nBuLi (2 equiv.)…”

Section: Directed Double Ortho-lithiations Of Phenylsulfoximines Amentioning

confidence: 99%

“…This led to the recovery of the corresponding non-deuterated heterocycles 58 and 45 in high yields. However, because of the relatively high NH-acidities estimated for the phenylogous sulfinamides [35] 58 and 45, [34] their reactions with nBuLi (1.1 equiv.) should have given the corresponding lithium salts 61 and 47 and their deuteration with D 2 O the corresponding heterocycles N-D-58 and N-D-45.…”

Section: Lithiation Of the Benzothiazepine And Benzothiazocine Soxidementioning

confidence: 99%

Sulfoximine‐Directed Single and Double ortho‐Lithiation: Stereoselective Rearrangements of o,o′‐Dilithiophenylsulfoximines to o,N‐Dilithiosulfinylanilines through Anionic Fries Rearrangements of o,o′‐Dilithiophenylsulfinamides

et al. 2011

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Treatment of various phenylsulfoximines with nBuLi (1 equiv.) at -78°C in THF resulted in single ortho-lithiations and gave the corresponding o-lithiosulfoximines. According to NMR spectroscopy, the o-lithiosulfoximines are generally stable at 0°C. The o-lithiosulfoximines were efficiently trapped through deuteration, alkylation, silylation, and phosphanylation. Treatment of cyclic phenylsulfoximines also containing H atoms at their α-positions with nBuLi (1 equiv.) at -78°C furnished the o-lithiosulfoximines with high selectivity, whereas similar treatment at -50°C to room temperature yielded the corresponding α-lithiosulfoximines. At elevated temperatures, o-lithiosulfoximines also possessing α-H atoms underwent quantitative o,α-transmetalation to afford the corresponding α-lithiosulfoximines. Treatment of α,α-disubstituted cyclic and α,α,α-trisubstituted acyclic phenylsulf-

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“…The dimethyloxazoline group is a relatively strong DMG 1b with a reported pK a of an ortho-H in 4,4-dimethyl-2-phenyloxazoline of 38.1. 6 Estimates of the pK a of the methyl group in toluene ranges from 39 to 45.2 using a variety of media and measurement procedures. 7 If under metalation conditions the pK a of the methyl group of 4,4-dimethyl-2-(o-tolyl)oxazoline is !40.1, then there is at least two orders of magnitude difference in the acidities of the two positions suggesting the possibility that selective ortho-lithiation can be achieved.…”

Section: Introductionmentioning

confidence: 99%

“…Metalation of the putative less acidic a-methyl was achieved under less stringent conditions (ether, À78 C). 3 As the measured pK a of the ortho-H in anisole is 39.0, 6 it was anticipated that greater difficulty would be encountered in discovering regioselective conditions for a-and, separately, for orthometalation of o-MA than for 4,4-dimethyl-2-(o-tolyl)oxazoline. 3 This preliminary analysis was based on the conjecture that the eOMe DMG would be at least as acidifying as the oxazoline DMG of their respective ortho-methyl groups.…”

Section: Introductionmentioning

confidence: 99%