Organic Synthesis International by Dr Anthony Melvin Crasto Ph.D, Worlddrugtracker, Million hits on google on all sites, One lakh connections worldwide. Pushing boundaries.Interaction site for Organic chemists worldwide, Mail me at email@example.com if you like me
Graphene oxide obtained by the Hummers method was discovered to be an efficient and recyclable acid catalyst for the conversion of fructose-based biopolymers into 5-ethoxymethylfurfural (EMF). EMF yields of 92%, 71%, 34% and 66% were achieved when 5-hydroxymethylfurfural (HMF), fructose, sucrose and inulin were used as starting materials, respectively.
Green Chem., 2013, 15,2379-2383 DOI: 10.1039/C3GC41109E, Communication
The three reaction modes open to this oxo-carbenium intermediate are:
in blue: capture of the carbocation by water or any suitable nucleophile through 5 to the 1,3-adduct 6.
in black: proton abstraction in an elimination reaction
to unsaturated compound 7. When the alkene carries a methylene group,
elimination and addition can be concerted with transfer of an allyl
proton to the carbonyl group which in effect is an ene reaction in scheme 6.
in green: capture of the carbocation by additional carbonyl
reactant. In this mode the positive charge is dispersed over oxygen and
carbon in the resonance structures 8a and 8b. Ring closure leads through
intermediate 9 to the dioxane 10. An example is the conversion of styrene to 4-phenyl-m-dioxane.
in gray: only in specific reactions and when the carbocation is very stable the reaction takes a shortcut to the oxetane 12. The photochemical Paternò–Büchi reaction between alkenes and aldehydes to oxetanes is more straightforward.
Many variations of the Prins reaction exist because it lends itself
easily to cyclization reactions and because it is possible to capture
the oxo-carbenium ion with a large array of nucleophiles. The halo-Prins
reaction is one such modification with replacement of protic acids and
water by lewis acids such as stannic chloride and boron tribromide. The halogen is now the nucleophile recombining with the carbocation. The cyclization of certain allyl pulegones in scheme 7 with titanium tetrachloride in dichloromethane at −78 °C gives access to the decalin skeleton with the hydroxyl group and chlorine group predominantly in cis configuration (91% cis). This observed cis diastereoselectivity
is due to the intermediate formation of a trichlorotitanium alkoxide
making possible an easy delivery of chlorine to the carbocation ion from
the same face. The trans isomer is preferred (98% cis) when the switch
is made to a tin tetrachloride reaction at room temperature.
The Prins-pinacol reaction is a cascade reaction of a Prins reaction and a pinacol rearrangement. The carbonyl group in the reactant in scheme 8 is masked as a dimethyl acetal and the hydroxyl group is masked as a triisopropylsilyl ether (TIPS). With lewis acid stannic chloride the oxonium ion
is activated and the pinacol rearrangement of the resulting Prins
intermediate results in ring contraction and referral of the positive
charge to the TIPS ether which eventually forms an aldehyde group in the final product as a mixture of cis and trans isomers with modest diastereoselectivity.
The Prins reaction is used in total synthesis of complex natural products, for example, in a key step of that of the synthesis of exiguolide:
^The Olefin-Aldehyde Condensation. The Prins Reaction. E. Arundale, L. A. Mikeska Chem. Rev.; 1952; 51(3); 505–555. Link
^4-Phenyl-m-dioxane R. L. Shriner and Philip R. Ruby Organic Syntheses, Coll. Vol. 4, p.786 (1963); Vol. 33, p.72 (1953). Article
^Syn- and Anti-Selective Prins Cyclizations of ,-Unsaturated Ketones to 1,3-Halohydrins with Lewis Acids R. Brandon Miles, Chad E. Davis, and Robert M. Coates J. Org. Chem.; 2006; 71(4) pp 1493 – 1501; Abstract
واکنش پرینز واکنش پرینز
واکنش پرینز (prins) یک واکنش آلی شامل افزایش الکتروفیلی یک آلدهید یا
کتون به یک آلکن یا آلکین با گرفتن نوکلئوفیل است. نتیجه واکنش بستگی به
شرایط واکنش دارد (طرح 1).در حضور آب و اسید پروتیک مانند سولفوریک اسید به
صورت واسطه واکنش و فرمالدهید محصول واکنش یک 3و1- دی ال 3 است.زمانی که
آب حضور ندارد آب زدایی برای تشکیل یک الکل آلیلی 4 اتفاق می افتد. با
مقدار اضافی از فرمالدهید و دمای کم واکنش محصول واکنش یک دی اکسان 5 است.
آب به وسیله استیک اسید جایگزین می شود استرهای مربوطه تشکیل می
The following essay describes
in broad terms the history of the discovery of Alimta. It was written as
a part of a brochure celebrating the dedication of Princeton’s
magnificent new chemistry building, completed by the end of 2010. The
building, recognized as perhaps the finest, best-equipped, and designed
facility for academic chemistry research in the country, was financed by
royalties to Princeton from sales of Alimta by Eli Lilly & Co., to
whom Princeton had given an exclusive license. The article was addressed
to a general audience; my lecture in Glasgow1 filled in the organic and
heterocyclic chemistry involved in the extensive explorations that
finally led to the discovery and synthesis of Alimta.
DNA double helix made up of two antiparallel strands complementary to
each other through specific base pairing of A with T and G with C codes
the key information necessary for synthesis and regulation of all
proteins and enzymes required of functioning of a cell from cell
division to cell differentiation and cell development. The discovery
also gave birth to the fields of molecular and structural biology, which
have been key to the genetic revolution that has resulted in the
development of vital products, ranging from hormones and enzymes to
therapeutic molecules and vaccines. The penultimate achievement stemming
from the discovery of DNA’s structure was the unraveling of the entire
human genome in 2001 and work continues unabated on the genomes of other
organisms. These discoveries have implications for our understanding of
diseases at the molecular level and, thereby, the development of cures.
Some of the most spectacular applications take advantage of the
self-assembling properties of the genetic molecule DNA to make
nonbiological novel generic materials.http://www.iupac.org/publications/ci/2013/3502/2_caruthers.html
by Shih-Yuan Liu and Michael Haley The 14th International Symposium on Novel Aromatic Compounds (ISNA-14)
was held 24–29 July 2011 in Eugene, Oregon, USA, on the campus of the
University of Oregon. Over 250 participants from 21 countries were
present, making this gathering the largest ISNA conference on North
American soil. The scientific program consisted of the 2011 Nozoe
Lecture presented by Peter Bäuerle (University of Ulm, Germany), 11
plenary lectures, 20 invited lectures, 29 contributed lectures, and 160
posters presented in two sessions. This IUPAC-sponsored symposium was
organized by Michael M. Haley (University of Oregon) and Benjamin T.
King (University of Nevada, Reno, USA).