enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Ring-closing metathesis - Wikipedia

    en.wikipedia.org/wiki/Ring-closing_metathesis

    Ring-closing metathesis (RCM) is a widely used variation of olefin metathesis in organic chemistry for the synthesis of various unsaturated rings via the intramolecular metathesis of two terminal alkenes, which forms the cycloalkene as the E-or Z-isomers and volatile ethylene.

  3. Enyne metathesis - Wikipedia

    en.wikipedia.org/wiki/Enyne_metathesis

    The ring-closing step takes place when this center reacts with the alkene group to a metallacyclobutane 4.5 as in a regular olefin metathesis reaction. The butadiene group forms in the last step with expulsion of a new methylene carbene, initiating the next cycle but now with R' = H and R' ' = H. This is the proposed "yne-then-ene" mechanism.

  4. Olefin metathesis - Wikipedia

    en.wikipedia.org/wiki/Olefin_metathesis

    The reverse reaction of RCM, ring-opening metathesis, can likewise be favored by a large excess of an alpha-olefin, often styrene. Ring-opening metathesis usually involves a strained alkene (often a norbornene) and the release of ring strain drives the reaction. Ring-closing metathesis, conversely, usually involves the formation of a five- or ...

  5. Alkyne metathesis - Wikipedia

    en.wikipedia.org/wiki/Alkyne_metathesis

    Alkyne metathesis can be used in ring-closing operations and RCAM stands for ring closing alkyne metathesis. The olfactory molecule civetone can be synthesised from a di-alkyne. After ring closure the new triple bond is stereoselectively reduced with hydrogen and the Lindlar catalyst in order to obtain the Z -alkene (cyclic E -alkenes are ...

  6. Grubbs catalyst - Wikipedia

    en.wikipedia.org/wiki/Grubbs_catalyst

    This catalyst is used in the ring-closing metathesis reaction in water of a diene carrying an ammonium salt group making it water-soluble as well. Ring closing metathesis reaction in water Third-generation Grubbs catalyst (fast-initiating catalysts)

  7. Carbonyl olefin metathesis - Wikipedia

    en.wikipedia.org/wiki/Carbonyl_olefin_metathesis

    The authors has proposed a stepwise mechanism. Based on this result, several methods have been developed in intramolecular systems to form the alkene bond through the same oxetane intermediate followed by subsequent formal retro [2+2] reaction thus accomplishing a formal olefin carbonyl ring closing metathesis transformation.

  8. 6 Big Shakeups Coming to Social Security in 2025 - AOL

    www.aol.com/6-big-shakeups-coming-social...

    Nearly 72.88 million Americans rely on Social Security for monthly income. The vast majority, about 65.5 million, collect Social Security benefits. Another 4.88 million receive Supplemental ...

  9. Ring forming reaction - Wikipedia

    en.wikipedia.org/wiki/Ring_forming_reaction

    A ring forming reaction or ring-closing reaction in organic chemistry is an umbrella term for a variety of reactions that introduce one or more rings into a molecule. A heterocycle forming reaction is a reaction that introduces a new heterocycle. [1] [2] Important classes of ring forming reactions include annulations [3] and cycloadditions ...