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At least 127 records · Page 7Linked to original sources
PubMed2006

Diastereomerically-specific zirconium complexes of chiral salan ligands: isospecific polymerization of 1-hexene and 4-methyl-1-pentene and cyclopolymerization of 1,5-hexadiene.

Chiral Salan ligands were found to wrap in a highly diastereoselective manner around zirconium leading to C2-symmetric complexes of predetermined chirality at the metal. These complexes led to active polymerization of higher olefins, their activity and isospecific induction depending on the nature of the phenolate substituents.

Journal Article↗
PubMed2006

Efficient synthesis of 1,3,5-trisubstituted (pyrrol-2-yl)acetic acid esters via dual nucleophilic reactions of sulfonamides or carbamate with 4-trimethyl-siloxy-(5E)-hexen-2-ynoates: Lewis acid catalyzed SN1 and intramolecular Michael addition.

[reaction: see text] Carbamates or sulfonamides have proven to regioselectively attack 2-propynyl-allyl hybrid cations, generated by the action of TMSOTf on 4-(trimethylsioxy)hex-5-en-2-ynoates, to afford conjugated 6-aminohex-4-en-2-ynoates in which an intramolecular amino-Michael reaction took place, leading to pyrrole frameworks. In particular, the sulfonamides gave 1-sulfonylpyrroles in one pot.

Journal Article↗
PubMed1999

Double anionic cycloaromatization of 2-(6-substituted-3-hexene-1,5-diynyl)benzonitriles initiated by methoxide addition.

[reaction: see text] Treatment of 2-((3Z)-undecene-1,5-diynyl)benzonitrile with 5 equiv of sodium methoxide in refluxing methanol for 16 h gave 1-pentyl-6-methoxyphenanthridine in 12% yield, 1-pentyl-6-phenanthridone in 6% yield, and 2-(2-pentyl-6-methoxyphenyl)benzonitrile in 4% yield. Under the same reaction conditions, methanolysis of several other benzonitriles gave similar results. Phenanthridine and biphenyl derivatives were obtained as the major products. A mechanism for this novel cycloaromatization reaction of enediynes is proposed.

Cyclization↗
PubMed2004

Non-aromatic endocyclic angle at the ring fusion with the aromatic ring in benzocyclopentene and -hexene, revisited.

X-ray geometries of monocycloalkenobenzenes with a fused-ring size of r = 5, 6 were obtained by the use of the Cambridge Structural Database. In contrast to Allen's study [Acta Cryst. (1981), B37, 900-906], the data were not averaged over exact or imposed m(ad) symmetry (m(ad) is the mirror plane going through the midpoint of the aromatic ring fusion bond and the aromatic bond parallel to it). The distribution of the non-aromatic endocyclic angle epsilon at the ring fusion clearly shows two and three, respectively, distinct curves for r = 5 and r = 6. The respective ranges are 104.3-112.6 and 104.4-123.2 degrees. If one of the C atoms directly attached to the aromatic ring is sp(2) hybridized, the bond length e between the aromatic ring and this atom is shortened by some 0.044 (15) and 0.027 (12) A for r = 5 and r = 6, respectively. However, for r = 5, e is only shortened by 0.030 (17) A when both C atoms directly attached to the aromatic ring are sp(2) hybridized. For r = 5, the endocyclic angle epsilon is 1.2 (13) degrees smaller at the side involving the sp(2) hybridized C atom.

Chemical Phenomena↗
PubMed1996

Photosynthetic photon flux, photoperiod, and temperature effects on emissions of (Z)-3-hexenal, (Z)-3-hexenol, and (Z)-3-hexenyl acetate from lettuce.

To investigate the effects of environment on plant volatile emissions, 'Waldmann's Green' leaf lettuce was cultivated under different levels of photosynthetic photon flux (PPF), photoperiod, and temperature. A modified growth chamber was used to sample plant volatile emissions nondestructively, over time, and under controlled conditions. Total volatile emission rates were significantly higher from lettuce cultivated under PPF of 360 or 200 micromoles m-2 s-1 compared to 105 micromoles m-2 s-1, and significantly higher under a 16-h photoperiod than an 8-h photoperiod. No differences were detected among emission rates from different temperature treatments. In controlled environments, emissions could be regulated by adjusting environmental conditions accordingly.

Air↗