Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• achieved in excellent yield using a [2 + 2] block glycosylation strategy. TEMPO-mediated selective oxidation of the primary alcohol of the tetrasaccharide derivative 8 to the carboxylic group followed by deprotection of the functional groups furnished target tetrasaccharide 1 as its 4-methoxyphenyl

• conversion of O-acetyl group to O-benzyl group [22], (iv) activation of glycosyl trichloroacetimidate and thioglycoside donors by perchloric acid supported on silica (HClO4–SiO2) [23][24][25][26], and late stage TEMPO mediated selective oxidation [27][28][29] of the primary hydroxy group to the carboxylic

• subjected to a reaction sequence involving (a) deacetylation using 0.1 M sodium methoxide in methanol; (b) TEMPO mediated selective oxidation [27][28][29] of the primary hydroxy group leaving secondary hydroxy groups unaffected in a phase transfer reaction condition and (c) removal of benzyl groups for

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• single diastereomer upon chelation with zinc chloride. TEMPO oxidation gave lactone 1, which corresponds to the reported structure of cephalosporolide H. A more detailed discussion is found in our earlier report [28]. Two mechanistic alternatives (Scheme 7) are proposed for the conversion of 6 → 17 in

Thermal rearrangement of tert-butylsulfinamide

• Veera Reddy Arava,
• Laxminarasimhulu Gorentla and
• Pramod Kumar Dubey

Beilstein J. Org. Chem. 2011, 7, 9–12, doi:10.3762/bjoc.7.2

• TEMPO a radical initiator (entries 22 and 23) or by a radical inhibitor 2,6-di-tert-butylphenol (entry 24). When the reagent 1 alone was subjected to thermal rearrangement (entry 1), complete consumption of starting material was observed. Only 27% product was isolated and 73% of the material was lost by

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP

• Olubummo Adekunle,
• Susanne Tanner and
• Wolfgang H. Binder

Beilstein J. Org. Chem. 2010, 6, No. 59, doi:10.3762/bjoc.6.59

Synthesis of gem-difluoromethylenated analogues of boronolide

• Jing Lin,
• Xiao-Long Qiu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2010, 6, No. 37, doi:10.3762/bjoc.6.37

• aldehyde 9 with the fluorine-containing building block 11 and the efficient construction of α,β-unsaturated-δ-lactones 15a–b via BAIB/TEMPO-procedure. Keywords: boronolide; gem-difluoromethylenated analogues; gem-difluoropropargylation; α,β-unsaturated-δ-lactones; Introduction (+)-Boronolide (1

• –quinoline system [26], leading to the expected alcohol 13a in 96% yield. Subsequent selective removal of the primary TBS group in 13a with D-camphor-10-sulfonic acid (CSA) yielded the diol 14a in 80% yield. As expected, treatment of compound 14a with 0.2 equiv of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO

• and the efficient construction of α,β-unsaturated-δ-lactones 15a–b via the BAIB/TEMPO-procedure. Boronolide (1), boronolide analogues 2–3 and gem-difluoromethylenated analogues 4–7. Retrosynthetic analysis of target molecules 4–7. Synthesis of target molecules 4–5. Synthesis of target molecules 6–7

Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• . Herein, we describe the application of titanium dioxide in conjunction with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) as an oxidant in the synthesis of quinoxalines, via the tandem oxidation process (TOP) (Scheme 1). Results and Discussion Titanium dioxide in the anatase phase is a

• positive holes to the surface and subsequent hydroxyl radical formation [24]. It is believed that a similar interaction is taking place in our system and in conjunction with TEMPO lead to the formation of keto-aldehydes or diketones, which are trapped in situ to produce the required products. In an attempt

• TEMPO for the selective oxidation of alcohols to aldehydes and ketones. In our studies we have been examining similar systems with a view to incorporating them into tandem type processes. Conclusion In summary, we have reported the use of titanium dioxide as a tandem oxidation catalyst, demonstrated by

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed- bed microreactor

• Andrew Bogdan and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2009, 5, No. 17, doi:10.3762/bjoc.5.17

• characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol

• 100 trials without showing any loss of catalytic activity. Keywords: alcohol oxidation; flow chemistry; heterogeneous catalysis; microreactors; TEMPO; Introduction Microreactors have gained attention because they can help run chemical transformations more efficiently, more selectively, and with a

• leaching nor the need for catalyst regeneration [22]. Nitroxyl radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), immobilized on silicates [23][24][25][26][27][28][29][30][31][32], fluorous supports [33], soluble and insoluble polymers [22][34][35][36], magnetic nanoparticles [37], and ionic