Amidines can be protonated by carboxylic acids to give amidinium carboxylates, and the ions can associate by forming multiple charge-assisted hydrogen bonds according to reliable motifs. Extended hydrogen-bonded networks can be constructed by treating suitable bis(amidines) with acids containing multiple carboxyl groups. To further explore the potential of this strategy, we have determined the structures of salts produced by treating 2,2′-bi-2-imidazoline, a cyclic bis(amidine), with oxalic, fumaric, terephthalic, and trimesic acids. The structures of the salts proved to incorporate features resulting predictably from the geometry of the ions and their ability to engage in charge-assisted hydrogen bonds.

Two bis(amidines), 2,2′-bi-2-imidazoline (BI) and fluoflavin (FF), were treated with phosphonic, phosphoric, and sulfonic acids in an effort to produce crystalline salts composed of ions linked by networks of charge-assisted hydrogen bonds. As intended, mixing bis(amidine) BI with 1,4-benzenediphosphonic acid and 1,3,5-benzenetriphosphonic acid yielded crystals of phosphonate salts of dication H2BI+2. Structural analyses showed that such salts tend to incorporate tapes composed of alternating dications and anions linked by multiple charge-assisted N–H···O hydrogen bonds of type R2 2(9) and R2 1(7). Typically, the ionic tapes are further connected to form sheets or other assemblies by additional O–H···O hydrogen bonds involving phosphonate anions. An analogous reaction of the more weakly basic bis(amidine) FF with 1,4-benzenedisulfonic acid yielded only a sulfonate salt of monocation HFF+; however, diprotonation could be achieved by phosphoric acid to produce a crystalline salt built from stacks of H2FF+2 dications linked to phosphate anions by charge-assisted N–H···O hydrogen bonds of type R2 2(8). Together, these results demonstrate that acids with multiple PO(OH)2 and SO2OH groups can react with bis(amidines) to produce salts with structural features resulting predictably from the geometry of the ions and their ability to engage in multiple charge-assisted hydrogen bonds according to standard patterns.

1-Iodoalkynes are formed in moderate to high yields from readily accessible benzylic and allylic alkyl bromides by a one-pot homologation/double elimination procedure with iodoform (CHI(3)). The developed conditions include facile purification and avoid the use of an excess of triphenylphosphine (PPh(3)), as described in classical Corey-Fuchs iodoalkynylation conditions. Replacing CHI(3) with CHI(2)Cl allows the isolation of the corresponding gem-(Z)-chloro-(E)-iodoalkene in good yield and stereoselectivity. Moreover, the use of benzhydryl bromides as nucleophiles enables the synthesis of trisubstituted alkenes under similar reaction conditions.

One-Pot Synthesis of 1-Iodoalkynes and Trisubstituted Alkenes from Benzylic and Allylic Bromides. -(PELLETIER, G.; LIE, S.; MOUSSEAU, J. J.; CHARETTE*, A. B.; Org. Lett. 14 (2012) 21, 5460-5467, http://dx.doi.org/10.1021/ol302544s ; Dep. Chem., Univ. Montreal, Montreal, Que. H3C 3J7, Can.; Eng.) -Jannicke 13-051