Sulphenylation and halogenation reactions leading selectively to cis-carbapenem precursors; stereospecific synthesis of (±)-6-epithienamycin

Copper(I)‐Catalyzed Asymmetric Interrupted Kinugasa Reaction: Synthesis of α‐Thiofunctional Chiral β‐Lactams

“…Azetidines of this sort are difficult to access by other methods. [1c] Through mCPBA oxidation, the sulfoxide (11) was formed in 77 % yield. When 4 a was treated with diethylaminosulfur trifluoride (DAST), an a-fluoro chiral b-lactam (12) was isolated in 92 % yield.…”

“…Herein, we describe the first three-component interrupted Kinugasa reaction, which quickly assembles terminal alkynes, nitrones, and sulfur electrophilies into enantioenriched a-thiofunctional chiral blactams. [11] As shown in Scheme 1, protonation of the four-membered enolate copper(I) intermediate (M 1 ) produces a 3,4-disubstituted lactam, the normal Kinugasa product. Herein, we propose an interrupted Kinugasa reaction with a sulfur electrophile introduced to intercept intermediate M 1 forming an a-thiofunctional multisubstituted b-lactam.…”

Olivanic acid analogues. Part 6. Biomimetic synthesis of (±)-PS-5, (±)-6-Epi-PS-5, and (±)-benzyl MM22381

“…Further elution of the original column provided the (2RS,3RS,SRS,6SR)-isomer (23a), again as a gum (0.205 g, 16%) (Found: M', 449.1241); v, , , 3450, 1750, 1725, 1670, 1610, 1 525,and 1 350cm-';6, 1.56-2.20(2H,m,CH2CHO), 1.94(3 H, s), 2.57-2.86 (4 H, m, 4-H2 and SCH,), 3.35 (2 H, q, J 6.5 Hz, NCH,), 3.35-4.1 (3 H, m, 3-, 5-, and 6-H), 4.27 (1 H, d, J 7 Hz, 2-H), 5. 28 (2 H, s, CH2Ar), 5.98 (1 H, br s, NH), 7.57 (2 H, J 9 Hz) and 8. 22 (2 H, J 9 Hz) (together AA'BB', ArH), and 9.73 (1 H, s, CHO).…”

“…9385; elution with EtOH-EtOAc (3 : 97)] unexpectedly gave (2RS,5RS,6RS)p- nitrobenzyl 3-(2-acetamidoethylthio)-4-chloro-6-ethyl-7-oxo-1 -azabicyclo[3.2.0]hept-3-ene-2-carboxylate (26a) as a gum (0.009 g, 15%), h,,,(EtOH) 264 nm; v, , , 3450, 1780, 1 755, 1 675, 1 610, 1 570w (vinyl sulphide), 1 525, and 1 350 cm-'; 6, 1.13 (3 H, t, J 7 Hz, MeCH,), 1.55-1.95 (2 H, m, MeCH,), 1.99 (3 H,s,Ac),m,SCH,),m,),4.66 (1 H,dd,J 6 and 4 Hz,5.31 (3 H,m,Ar),5.83 (1 H, br s, NH), and 7.55 (2 H, J 9 Hz) and 8. 28 (2 H, J 9 Hz) (together AA'BB', ArH); m/z (EI) M + , 467.469. C20H22ClN306S requires M , 467.469; (NH, gas CI) MNH4+, 485.487.…”

Novel Metal- and Mineral-Acid–Free Synthesis of Organic Ammonium Tribromides and Application of Ethylenephenanthrolium Bistribromide for Bromination of Active Methylene Group of 1,3-Diketones and β-Ketoesters

“…[14] Such brominated products often serve as useful building blocks in the synthesis of natural and non-natural products. [15] Most commonly used reagents to access those monobrominated products include Br 2 , [16] H 2 O 2 -HBr, [17] NBS, [18] CuBr 2 -Koser's reagent, [14a] NaOBr in acetone/AcOH, [19] NH 4 Br-oxone, [20] bromodimethylsulfonium bromide [21] (BDMS) etc.…”