Cyclic reactions with diazoalkanes

Substituted 1,4-diazooxides rect with secondary aliphatic amine to give the corresfxjnding triazene (diazoamino compounds) in high yield, while the products with primary amine are surprisingly unstable and deompose by a radical mechanism. Reactions with diazoalkanes yield asymmetrical azine 29 (15) in the case of 1,4-diazooxide, and cyclic benzoxadiazines 30 with 1,2-diazooxides (16) . 

Heterocyclic substituted tetraorganogermanes are prepared by introduction of the cyclic moiety with organolithium derivatives (l) by forming the heterocycle in a side chain reaction with diazoalkane (II) or by dehydration with hydrogen sulfate (III). The compounds are prepared by methods in the following scheme and are compiled in Table k on page 19-... 

Bordoni, S., Busetto, L., Cassani, M.C., Albano, V.G. and Sabatino, P. (1994) Reactions of [Au(C6F5)(SC4Hs)] with diazoalkanes. Synthesis and molecular structures of [cyclic] [Au(C6F5)(Ph2C NN CPh2)[. Inorganica Chimica Acta, 222 (1-2), 267-273. 

The availability of phosphaalkenes led to a second route to phosphiranes with diazoalkanes as cycloaddition partners compare with Scheme 14. The first formed 4,5-dihydro-3//-l,2,4-diazaphospholes 43 decompose under the influence of light and extrusion of nitrogen to form the bis(methylene) phosphoranes 44, which cyclize in a 47t-electro-cyclic closure to the phosphiranes 45 (Scheme 17) <1996CHEC-II(I)298>. For the theoretical background, see Section 1.08.2.1.1, and for analogous reactions see <1995CC25> and <1997CB779>. 

Addition of the diazoalkane nucleophile is followed by an reaction with ring-closure or a homologous ketone is formed with a 1,2-alkyl rearrangement (shift). Spirooxiranes are produced from cyclic ketone derivatives with diazomethane (Eq. 86). ... 

In the rearrangement reaction, the multistep sequence offers the definite advantage of avoiding the polyhomologation of cyclic ketones, often encountered with diazoalkanes due to the presence of the reagent with both the starting and reananged ketone. 

Cyclic disulfanes (376) react with diazoalkanes (377) via their corresponding carbenes under insertion to yield (378) (Equation (81)) Cu(I)Cl or dimeric rhodium acetate is used in these reactions as a catalyst <85TL5187, 88T3159>. 

The reaction system (6-37) includes the thermal azo-extrusion of a cyclic azo compound to a cyclopropane derivative and the direct formation of cyclopropanes, catalyzed by metal complexes. Synthetic routes to cyclopropane derivatives became an important subject in the last two decades, and one frequently used method is the 1,3-dipolar cycloaddition of a diazoalkane to an alkene followed by thermal or photolytic azo-extrusion of the 4,5-dihydro-3//-pyrazole formed to the cyclopropane derivative (6-37 A). This route can be followed in many cases without isolation, or even without direct observation, of the 4,5-dihydro-3//-pyrazole. Therefore, it is formally very similar to cyclopropane formation from alkenes with diazoalkanes, in which a carbene is first formed by azo-extrusion of the diazoalkane (see Sect. 8.3). As shown in pathway (6-37 B), this step can be catalyzed by copper, palladium, or rhodium complexes (see Sects. 8.2, 8.7, and 8.8). There are cases where it is not clearly known whether route A or B is followed. Scheme 6-37 also includes... 

In the context of ring enlargements by the Tiffeneau rearrangement, we have already mentioned in Section 7.7 the ring enlargement of cyclic ketones by reaction with diazomethane (see Scheme 7-48). This process is, of course, also an electrophilic substitution at the C(a)-atom of a diazoalkane. 

Finally, ring expansions of cyclic ketones are an important method for the preparation of carbocyclic systems. Diazoalkanes allow this reaction to occur and involve C—C bond formation. When combined with carefully chosen organoaluminum compounds, this process can be performed in a highly stereoselective fashion (equation 148)541. 

The three-, four-and five-membered cyclic sulfones have some interesting reactions. Three-membered ring sulfones, called thiirane-1,1-dioxides or episulfones, can be prepared by reaction of a diazoalkane, e.g. (160), with sulfur dioxide (Scheme 63). The reaction affords a mixture of the cis-episulfone (161) and trans-episulfone (162), and both isomers can be isolated by fractional crystallisation at low temperature. Another method of preparation of episulfones is by treatment of a diazoalkane with a sulfonyl chloride (containing a-hydrogen atoms) and a tertiary amine (Scheme 64). Both these syntheses involve the formation of the highly reactive sulfene intermediate (163) (see Chapter 7, p. 114) episulfones on warming eliminate sulfur dioxide to form the alkene (164) as indicated in Scheme 64.7... 

Under the usual conditions one equivalent of the diazoalkane is consumed by the liberated acid but this can be avoided by use of an added base such as triethylamine/ Cyclic a-diazoketones, which are not available from acid chloride, can be prepared by reaction of a nucleophilic derivative such as the a-hydroxymethylene enolate with arylsulfonyl azides. Several combinations of carbon nucleophile and sulfonyl... 

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