Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• the α-position of the carbonyl group (93% D). The syn selectivity was slightly decreased due to the deuterium isotope effect: Slower D-trap caused isomerization of organocopper intermediates (vide infra). This experimental result indicates that t-BuOH acts as a proton source. A possible mechanism for

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• aromatics using THF-d8 was reported [88]. We explain the reduced yield of 6-D (48% yield) and the formation of tar products by hydrogen atom abstraction from 3 or 6 and subsequent polymerization. No significant amounts of double deuterated products were detected. The kinetic isotope effect was determined

Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp²)–H activation/C–O formation

• Seohyun Shin,
• Dongjin Kang,
• Woo Hyung Jeon and
• Phil Ho Lee

Beilstein J. Org. Chem. 2014, 10, 1220–1227, doi:10.3762/bjoc.10.120

• ranging from 50% and 63%. We carried out kinetic isotope effect (KIE) studies to prove the reaction mechanism (see Scheme 8). The required deuterium-labeled 2-(phenyl)phenylphosphonic acid monoethyl ester 1a-[D5] was efficiently prepared by a Suzuki reaction of deuterated bromobenzene (6) with 2

• PhI(OAc)2. However, no cyclized product was observed. This result indicates that the C–O reductive elimination from Pd(II) is not favorable. Because both the intermolecular and intramolecular competition experiments exhibited no significant kinetic isotope effect (kH/kD = 1.0 and 0.6; Scheme 8), we

Molecular recognition of isomeric protonated amino acid esters monitored by ESI-mass spectrometry

• Andrea Liesenfeld and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 825–831, doi:10.3762/bjoc.10.78

• ether moiety which would largely rule out any isotope effect (motif B in Figure 6). Conclusion We have synthesised two new functionalized crown ethers 1 and 2 both bearing a 9,9’-spirobifluorene moiety and studied their ability to differentiate between the constitutional isomers L-leucine, L-norleucine

[²H₂₆]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus

• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319

• Streptomyces griseus. This compound represents the first completely deuterated terpene obtained by fermentation. Despite a few previous reports in the literature the operability of this approach to fully deuterated compounds is still surprising, because the strong kinetic isotope effect of deuterium is known

• eight to ten days of incubation until fully grown, reflecting the significantly slowed metabolism due to a strong deuterium kinetic isotope effect. After full growth of the culture the volatiles emitted by S. griseus were collected on charcoal traps by use of a closed-loop stripping apparatus (CLSA) [25

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• induction period and demonstrated the involvement of radical species in the reaction. The authors proposed a mechanism accounting for the EPR profile of the reaction and for the results of kinetic isotope effect experiments (Figure 21). In this mechanism, rhenium intervenes in the initiation step. It acts

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Presence or absence of a novel charge-transfer complex in the base-catalyzed hydrolysis of N-ethylbenzamide or ethyl benzoate

• Shinichi Yamabe,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2013, 9, 185–196, doi:10.3762/bjoc.9.22

• unclear in the following points: 1. The rate-determining step of the ester hydrolysis was suggested to be the nucleophilic OH− addition to the carbonyl carbon according to the kinetic result of the heavy-atom isotope effect [17]. On the other hand, in the hydrolyses of a series of toluamides (Me–C6H4–C(=O

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• (Scheme 2) [16]. The observation of a high kinetic isotope effect is suggestive of a concerted metalation–deprotonation mechanism, as first suggested for Pd(II) complexes, in which a pivalate ligand behaves as a proton acceptor via a six-membered transition state [17]. However, addition via a transient Au

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• enantioselectivity in the electrophilic substitution of 73, Hoppe made use of an extremely high kinetic H/D isotope effect observed for deprotonation in similar compounds [65]. Reaction of a test substrate demonstrated an isotope effect of kH/kD ≥ 100. A racemic mixture of 77 was lithiated in the presence of

Catalysis: transition-state molecular recognition?

• Ian H. Williams

Beilstein J. Org. Chem. 2010, 6, 1026–1034, doi:10.3762/bjoc.6.117

• an archetypal reaction in organic chemistry and an important process in biochemistry. Catechol-O-methyl transferase (COMT) catalyses methyl transfer from S-adenosylmethionine (SAM) to a catechol (Scheme 1), and this reaction manifests an unusually large inverse secondary kinetic isotope effect as

• compared with a model, uncatalysed reaction in solution: the isotope effect VCH3 /VCD3 = 0.83 ± 0.05 for methylation of 3,4-dihydroxyacetophenone with SAM at 37 °C catalysed by COMT was found [11] to be more inverse than the value of kCH3 /kCD3 = 0.97 ± 0.02 for methylation of methoxide ion by S

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• . They rationalized that monodeuterio derivative 109 should be a better substrate, having a slower indole deprotonation rate, due to a primary kinetic isotope effect. Accordingly, treatment of the monodeuterio derivative 109 with methyl lithium followed by quenching with phenylselenium chloride yielded