Cycloalkenes into ketones

OL-Bromo ketones. The reagent in combination with triethylamine converts oxides of alkenes and oxides of five- to seven-membered cycloalkenes into a-bromo ketones in 70-80% yield, Morpholinoenamines under these conditions are also converted into a-bromo ketones. 

Some attempts have been made to modify diastereoselectivity by introducing chiral substituents into the azide precursor of the nitrene (see Sch. 28) [22,43,44]. The photocycloaddition of acyl nitrenes bearing chiral substituents to cycloalkenes having enantiotopic faces such as compound 85, or prochiral ketones, can lead to the formation of two diastereomers. However, this chiral induction has not been observed in the reaction of the nitrenes... 

Allylic diethylboranes.1 These boranes (2) can be prepared from 1-methyl-cycloalkenes and 2-alkenes by metallation with trimethylsilylmethylpotassium2 followed by reaction with 1. The products react with acetaldehyde to form homoallylic alcohols (3), which can be converted into a,(3- and p,y-unsaturated ketones. 

A practical synthesis of 1,3-OX AZEPINES VIA PHOTOISOMERIZATION OF HETERO AROMATIC V-OXIDES is illustrated for 3,1-BENZOXAZEPINE. A hydroboration procedure for the synthesis of PERHYDRO-9b-BORAPHENALENE AND PERHYDRO-9b-PHEN-ALENOL illustrates beautifully the power of this methodology in the construction of polycyclic substances. The conversion of LIMONENE TO p-MENTH-8-EN-YL METHYL ETHER demonstrates a regio-and chemoselective method for the PHOTOPROTONATION OF CYCLOALKENES. An efficient method for the conversion of a ketone to an olefin involves REDUCTIVE CLEAVAGE OF VINYL PHOSPHATES. A mild method for the conversion of a ketone into the corresponding trimethylsiloxy enol ether using trimethylsilyl acetate is shownforthe synthesis of (Z)-3-TRIMETHYLSILOXY-2-PENTENE. 

Similar to the benzynezirconocene, cyclohexyne, cyclopen-tyne, alkyne, alkene, cycloalkene zirconocenes, and related species insert various substrates such as alkynes, alkenes, aldehydes, ketones, nitriles or phosphaalkynes. They lead in general five-membered zirconacycles, which can be converted by transmetalation or exchange reactions into fused-ring aromatic or heterocyclic compounds. The extension of this chemistry to heterobenzyne complexes can be realized, for instance, in phosphinine compounds.Consequently, under mild conditions, -phosphabenzyne-zirconocene complexes are formed and can be isolated either as PMeg adducts or as dimers when the elimination reaction is carried out without added phosphane (Scheme 28). 

Cycloalkenes are converted into a,B-unsaturated ketones using Bu "00H in the presence of catalytic amounts of [Cr(C0)g]. Some secondary alcohols have been shown to be inert to these oxidizing... 

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