Reactions cleaving carbon-carbon bonds with the assistance of transition metals as catalyst have provided various molecular transformations that are otherwise difficult to execute, opening a scenic avenue along organic synthesis. Construction structural motifs like medium-sized carbocycles and chiral quaternary carbon centres been set within an access such paradoxical approaches in past decade.

3,4-Dihydrocoumarin derivatives were synthesized in a highly enantioselective manner from 3-(2-hydroxyphenyl)cyclobutanones through carbon−carbon bond cleavage. A cascade reaction with electron-deficient alkenes introduced at the 5-position of dihydrocoumarins.

Cyclobutanones reacted with alkynes in the presence of nickel(0) catalysts to produce cyclohexenones. Oxidative cyclization carbonyl group cyclobutanone and alkyne was followed by beta-carbon elimination from resulting oxanickelacyclopentene subsequent reductive elimination. This reaction achieves a formal insertion between carbon alpha-carbon, providing six-membered carbocyclic skeleton.

Cyclobutanones underwent a formal [4 + 2 2] annulation reaction with 1,6- and 1,7-diynes in the presence of nickel(0) catalysts to provide bicyclic eight-membered ring ketones. The proceeds through ring-expansion oxanickelacycloheptadiene via beta-carbon elimination form nine-membered nickelacycle. This employing cyclobutanones as C4 unit constructs cyclooctadienone cores one synthetic step.

(Triorganosilyl)pinacolboranes were prepared by reaction of triorganosilyllithium reagents with pinacolborane or isopropoxypinacolborane in high yield. The also is applicable to synthesis 2-(triorganosilyl)-4,4,6-trimethyl-1,3,2-dioxaborinane. A new germylborane derivative was similarly from the corresponding germyllithium.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPalladium- and Platinum-Catalyzed Silaboration of Methylenecyclopropanes through Selective Proximal or Distal C−C Bond CleavageMichinori Suginome, Takanori Matsuda, Yoshihiko ItoView Author Information Department Synthetic Chemistry Biological Graduate School Engineering Kyoto University, 606-8501, Japan Cite this: J. Am. Chem. Soc. 2000, 122, 44, 11015–11016Publication Date (Web):October 21, 2000Publication History Received7 August...

A chiral all-carbon benzylic quaternary carbon center is created by the asymmetric intramolecular addition/ring-opening reaction of a boryl-substituted cyclobutanone, which involves enantioselective β-carbon elimination from symmetrical rhodium cyclobutanolate. The was successfully applied to synthesis sesquiterpene, (−)-α-herbertenol.

[reaction: see text] Silicon-bridged 1,6-diynes underwent [2 + 2 2] cycloaddition with alkynes in the presence of an iridium(I)-phosphine catalyst to afford densely substituted silafluorene derivatives. Extended skeletons were constructed by tetraynes.

Abstract New catalytic reactions in which transition-metal cyclobutanolates undergo β-carbon elimination have been developed our laboratory. Rhodium(I) cyclobutanolate generated by the addition of an arylrhodium(I) species to a cyclobutanone undergoes cause ring opening four-membered carbocyclic framework. The synthetic potential ring-opening process through has demonstrated its application ring-expansion reaction forming seven-membered ring. Furthermore, formal alkyne insertion into...

Double insertion of alkynes into the Si−B bond (dimethylphenylsilyl)pinacolborane proceeded in presence nickel(0) catalysts to give cis,cis-1-silyl-4-boryl-1,3-butadiene derivatives a regio- and stereoselective manner. Involvement (silyl)(2-boryl-1-alkylvinyl)nickel(II) intermediates silaborative dimerization reaction was suggested by regiochemical preference as well on basis reactions corresponding germylborane with Ni, Pd, Pt catalysts.

Cyclobutanones react with arylboronic acids in the presence of a catalytic amount Rh(I) complex to afford butyrophenone derivatives through addition an arylrhodium(I) species carbonyl group, followed by ring-opening resulting rhodium(I) cyclobutanolate. [reaction: see text]

Ever-increasing circles: Seven-membered-ring ketones are constructed by a rhodium(I)-catalyzed arylative ring-expansion reaction of alkyne-substituted aryl cyclobutanones, in which two CC bond-forming and one bond-cleaving events occur consecutively (see scheme). Medium-sized carbocyclic ring systems often present as the structural core natural products interesting biological activities. Thus, development new synthetic methods for medium-sized rings has been prime targets organic...

Spiropentanes undergo carbonylation under an atmosphere of carbon monoxide in the presence a rhodium(I)−phosphine catalyst, giving 3-methylcyclopent-2-enones. The catalytic cycle involves two mechanistically different carbon−carbon cleavage processes. spiropentane was successfully applied to short synthesis (±)-β-cuparenone.

Reaction of triethylgermane and alkynes in the presence a ruthenium catalyst occurred trans fashion. The ruthenium-catalyzed trans-hydrogermylation 1,3-diynes with dihydrogermanes afforded 2,5-disubstituted germoles good yield through two fold addition process. hydrogermylation reaction was successfully applied to synthesis 2,2′-bigermole.

Dihydrosilanes undergo double trans-hydrosilylation with 1,4-diarylbuta-1,3-diynes in the presence of a cationic ruthenium catalyst to afford 2,5-diarylsiloles: particular, 9-silafluorene is good hydrosilylating agent produce spiro-type siloles yield.

Thraustochytrids are known to synthesize PUFAs such as docosahexaenoic acid (DHA). Accumulating evidence suggests the presence of two synthetic pathways in thraustochytrids: polyketide synthase-like (PUFA synthase) and desaturase/elongase (standard) pathways. It remains unclear whether latter pathway functions thraustochytrids. In this study, we report that standard produces PUFA Thraustochytrium aureum ATCC 34304. We isolated a gene encoding putative Δ12-fatty desaturase (TauΔ12des) from T....

ABSTRACT A versatile transformation system for thraustochytrids, a promising producer polyunsaturated fatty acids and acid-derived fuels, was established. G418, hygromycin B, blasticidin, zeocin inhibited the growth of indicating that multiple selectable marker genes could be used in system. neomycin resistance gene ( neo r ), driven with an ubiquitin or EF-1α promoter-terminator from Thraustochytrium aureum ATCC 34304, introduced into representatives two thraustochytrid genera,...

1,4-Rhodium migration occurs twice during the course of rhodium-catalysed arylative ring-opening/spirocyclisation reaction (3-arylcyclobutylidene)acetates with sodium tetraarylborates to afford ketones possessing a 1,1'-spirobiindane skeleton.

Thraustochytrids, marine protists known to accumulate polyunsaturated fatty acids (PUFAs) in lipid droplets, are considered an alternative fish oils as a source of PUFAs. The major produced thraustochytrids palmitic acid (C(16:0)), n - 6 docosapentaenoic (DPA) (C(22:5)(n) (- 6)), and docosahexaenoic (DHA) (C(22:6)(n) 3)), with eicosapentaenoic (EPA) (C(20:5)(n) 3)) arachidonic (AA) (C(20:4)(n) 6)) minor constituents. We attempted here alter the composition through expression Δ5 desaturase...

The rhodium-catalyzed phenylcyclobutane-to-indane transformation proceeds<italic>via</italic>consecutive chelation-assisted C–C bond cleavage and intramolecular C–H cleavage.

We developed rhodium-catalyzed alkoxylcarbonylation/acylation of indolines using anhydrides as a safe and easy-to-handle carbonyl source. This catalytic process represents an additive- CO-free carbonylation, establishing simple straightforward protocol for synthesizing C7-carbonylated indolines. Notably, this reaction provides successful example C-H acylation that results in the formation α-branched ketones, which were difficult to prepare by previously reported analogous reactions.

This paper reports a direct α-(hetero)arylation of acrylamides through an inverse electron-demand nucleophilic addition, specifically anti-Michael-type addition. The introduction quinolyl directing group facilitates the addition (hetero)arenes to α-position acrylamides. effectively suppresses undesired β-hydrogen elimination and is removable for subsequent derivatization. presented method provides atom economical synthesis α-(hetero)arylamide with high degree functional tolerance.

Transition-metal-catalyzed asymmetric allylic substitution provides an efficient route to chiral organic molecules featuring allyl moiety, key intermediates in the synthesis of biologically active compounds. However, use unsymmetrical 1,3-disubstituted electrophiles has been severely constrained by challenges achieving both regio- and stereoselectivity simultaneously. Herein, we present γ-silyl-substituted acetates as highly effective for a enantioconvergent hydroallylation, enabling...

Transition‐metal‐catalyzed asymmetric allylic substitution provides an efficient route to chiral organic molecules featuring allyl moiety, key intermediates in the synthesis of biologically active compounds. However, use unsymmetrical 1,3‐disubstituted electrophiles has been severely constrained by challenges achieving both regio‐ and stereoselectivity simultaneously. Herein, we present γ‐silyl‐substituted acetates as highly effective for a enantioconvergent hydroallylation, enabling...