منابع مشابه
Caryolene-forming carbocation rearrangements
Density functional theory calculations on mechanisms of the formation of caryolene, a putative biosynthetic precursor to caryol-1(11)-en-10-ol, reveal two mechanisms for caryolene formation: one involves a base-catalyzed deprotonation/reprotonation sequence and tertiary carbocation minimum, whereas the other (with a higher energy barrier) involves intramolecular proton transfer and the generati...
متن کاملCarbocation branching observed in a simulation.
We have observed the branching rearrangement of a straight-chain secondary carbocation (C9H19+) in an ab initio molecular dynamics (AIMD) reverse-annealing (rising-temperature) simulation. The mechanism observed is one involving closed (protonated-cyclopropane) structures, previously observed in traditional geometry optimization calculations. However, the simulations give us a better understand...
متن کاملThiamin phosphate synthase: the rate of pyrimidine carbocation formation.
Carbocations have fascinated organic chemists for almost a century, and the properties of this reactive intermediate have been thoroughly studied.1 Carbocations have been proposed as intermediates in several enzyme-catalyzed reactions, such as the prenyl transfer and cyclization reactions involved in terpene biosynthesis,2,3 the pyrrole tetramerization involved in porphyrin biosynthesis,4 the g...
متن کاملOn the tunneling instability of a hypercoordinated carbocation.
C(CH3)5(+), a pentacoordinate carbocation, was recently described as a "fleeting" molecule, that is, stable only at low temperatures. Herein it is shown using theoretical methods that, owing to carbon tunneling, the molecule is not persistent even at 0 K. One possible way to lengthen its lifespan is by deuterium substitution, in spite of the fact that no bond to hydrogen is broken.
متن کاملMigration of methylethynyl group in a long-lived carbocation.
Degenerate 1,2-shift of methylethynyl group in long-lived 9,10-dimethyl-9-methylethynyl-phenanthrenium ion has been detected by NMR. This is the first example of ethynyl migration in a long-lived carbocation.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Synthesis
سال: 2005
ISSN: 0039-7881,1437-210X
DOI: 10.1055/s-2005-923539