Expedious synthesis of polyhydroxylated selena and thia-heterocycles via Se and S-ring closure of α,ω-dibromoalditols

Towards crystal engineering of solid-state polymerization in dibromothiophenes

“…Experimental section meso-Tetrahydrothiophen-3,4-diol (c) was prepared according to Benazza et al from the meso-erithritol with 56% overall yield. 24 Diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate was prepared according to Overberger and Lal from diethyl thiodiglycolate and diethyl oxalate with 80% yield. 25 Synthesis EDOT-R-COOEt (1a-c).…”

Sulfur-capped cyclodextrins: a new class of cavitands with extroverted as well as introverted donor functionalities

“…The synthesis of both ligands 1 and 2{ is related to that described previously for 'phosphinidene'-capped CDs. 8 Thus, reaction of A,B-dimesylated precursor 3 with an excess of the soft nucleophile 12 Na 2 S?9H 2 O in DMSO (method A) afforded 1 in nearly quantitative yield (Scheme 1). The synthesis of the C 2 -symmetrical ligand 2 proved to be more challenging as treatment of A,B,D,E-tetramesylate 4 with the same dianion resulted not only in the capping of adjacent glucose units, but also in some A,C-capping.…”

Alditol thiacrowns via a ring-closing metathesis of carbohydrate-derived α,ω-dithioallylethers

“…It is well-known that this type of substrate is difficult to isolate as they are prone to undergo an O-heterocyclization, under the reaction conditions of the direct halogenation. 18 We have however demonstrated that electron-withdrawing cyclic intermediates, such as the cyclic imminium salts obtained from either the Viehe-Janouzek salt, 19 the acetoxonium ion from acetylbromide (AcBr), 20 or cyclic thionocarbonates, 22 allow this unwanted side-reaction to be effectively circumvented. Thus, under the well-established experimental conditions using AcBr, selective 1,6-bisbromination occurs (via the corresponding acetoxonium ion) as expected to give the target α,ω-dibromoalditols 1 (xylo), 3 (ribo), 5 (D,L-threo), 7 (erythro), 9 (D-manno), and 11 (D-gluco) in good yields, starting from the appropriate sugars substrates ( Table 1, Column 1).…”