Facile and stereoselective synthesis of (E)-vinyl bromides by microwave-induced reaction of 1,1-dibromoalkenes using a diethyl phosphonate/EtONa/EtOH system

Experimental and theoretical studies on nickel–zinc-catalyzed cross-coupling of gem-dibromoalkenes with P(O)–H compounds

A new stereoselective one-pot protocol for the preparation of E-alkenyl-phosphorus compounds under catalysis of an inexpensive nickel–zinc catalyst system has been developed, which provides a potential useful method for C–P bond formation.

Decarboxylative Bromination of Cinnamic Acids by 2-Iodoxybenzoic Acid with Tetrabutylammonium Bromide

The decarboxylative bromination of cinnamic acids using the hypervalent iodine reagent 2-iodoxybenzoic acid with tetrabutylammonium bromide is described, providing good to excellent yields of bromostyrenes. Bromostyrenes are useful coupling components in a wide range of transition metal-catalysed coupling reactions.

Convenient one-pot synthesis of (E)-beta-aryl vinyl halides from benzyl bromides and dihalomethanes

(E)-beta-aryl vinyl iodides are synthesized in high yield with excellent stereoselectivity from benzyl bromides by a one-pot homologation/stereoselective elimination procedure. Convenient conditions involving the anion of diiodomethane and an excess of base provide complete consumption of the benzyl bromide and elimination from a diiodoalkane intermediate. Similar conditions provide (E)-beta-aryl vinyl chlorides and bromides by employing the anions of ICH(2)Cl or CH(2)Br(2). The functional group tolerance and facile purification allows rapid access to a wide range of functionalized vinyl halides.

Microwave-assisted rapid cyclization of lapachol, a main constituent ofHeterophragma adenophyllum

Cyclization reactions of lapachol (1) isolated from Heterophragma adenophyllum have been studied under microwave irradiation under different conditions using alumina (acidic, basic and neutral)/silica gel/montmorillonite (KSF and K-10) as solid support along with neat reaction using 2-3 drops of DMF giving naturally occurring dehydro-alpha-lapachone (2), alpha-lapachone (3), beta-lapachone (4) depending upon the nature of support and irradiation time. A novel naphthoquinone derivative adenophyllone (5) can be synthesized from lapachol using DMF under microwaves.

Stereoselective Synthesis of (E)- and (Z)-.BETA.-Bromostyrene Containing Trifluoromethyldiazirine for Photoaffinity Labeling

Summary A convenient procedure for the synthesis of (E)- and (Z)-beta-bromostyrene containing trifluoromethyldiazirine is described, which involves the stereoselective reduction of the corresponding trifluoromethyldiazirinyl beta,beta-dibromostyrene without damaging the photophor. The synthetic route easily introduced deuterium, which can be utilized for the detection of a photolabeled component by MS spectrometry, after construction of a trifluoromethyldiazirinyl skeleton.

High Stereoselective Preparation of O-Protected 2-Trifluoromethyl 3-Bromoallylic Alcohols from 1,1-Dibromo-1-alkenes

A highly stereoselective lithium-bromine exchange reaction of 2-trifluoromethyl-3,3-dibromoallylic alcohols is described. (E)- and (Z)-2-trifluoro-3-bromoallylic alcohols were obtained in THF and hexane, respectively. The lithium carbenoid intermediate was stable even at -40 degrees C and could be trapped by various electrophiles to afford functionalized 2-trifluoromethyl-3-bromoallylic alcohols. [reaction: see text]