Reactions of aldehydes with hydrazine hydrochlorides in the presence of dipolarophiles: intra- and intermolecular [3+ + 2] cycloadditions

Abstract

The reaction of 2 molar equiv of several 2-(alkenyloxy)-l-naphthaldehydes (2) with hydrazine dihydrochloride (3) and subsequent treatment of the mixture with triethylamine lead to intramolecular [3+ + 2] criss-cross cycloadducts 5, 2:1 molar products of 2 and 3, in high yields. On the other hand, naphtho [l',2':5,6]pyrano-[4,3-c]pyrazoles 11 and 12, equimolar products of 2 and 3, were obtained by a similar series of reactions using a large excess of 3. Many pyrazolium chlorides (25), 2,2-dimethyl derivatives of 11, were prepared in high yields from the equimolar reaction of 2 with 1,1-dimethylhydrazine hydrochloride (24). -Phenyl, iV-decyl, and JV-dodecyl derivatives 29,31, and 32, respectively, of 25 were also prepared from the reaction using the corresponding AT-phenyl, iV-decyl, and TV-dodecyl derivatives of 24. Similarly, 1,2-dimethyl derivatives 41 of 11 were also prepared from an equimolar reaction of 2 with 1,2-dimethylhydrazine dihydrochloride. Intermolecular cycloadducts corresponding to these intramolecular ones were also obtained by the reactions of benzaldehyde with these hydrazine hydrochlorides Cycloaddition Routes to Azaanthraquinone Derivatives. 2. Use of Aza Dienes1

Intra–Intermolecular Criss‐cross Cycloaddition of Nonsymmetrical Allenylazines with Fluorinated Enones as an Initial Step in the Synthesis of4H‐Pyrrolo[1,2‐b]pyrazoles

“…[3,7,8] The second group may be considered as an intramolecular cycloaddition. Depending upon the regioselectivity of the reaction, we can observe formation of laterally [9,10] or centrally [11,12] fused heterocyclic compounds. The third group is a combination of the first and the second approaches: a combined intra-intermolecular cycloaddition.…”

Intramolecular Hydro‐N‐alkylation of Hydrazones and Oxime Ethers: Synthesis of Novel D‐Secoestrone Isoquinuclidines via Domino 1,5‐Hydride Shift/Cyclization

“…Reaction of monosubstituted hydrazones 10b-l with BF 3 ·OEt 2 results in ionic intermediates 22b-l, which can undergo tautomerization to give the quasi-azomethine imine 1,3-dipolar intermediates 23b-l. [15] Coordination to the Lewis acid of phenylhydrazones containing an electron-donating group (CH 3 or OMe) on the aromatic ring, as in 10d or 10e, is presumed to be somewhat more favorable than that of phenylhydrazones with an electronwithdrawing group (NO 2 , CN, CF 3 ) in 10f-i or of acetylhydrazone 10b. [16] Nevertheless, complexation and the following N,NЈ-proton shift are assumed to occur under the given reaction conditions to afford intermediates 23b-l.…”

Organocatalyzed Carbonyl–Olefin Metathesis

“…the simple hydrazine catalyst 10, the carbonyl-olefin metathesis was demonstrated for a range of aryl and heterocyclic aldehydes (11) in generally good to excellent yields (Scheme 5). An inverse correlation between the electron-rich character of 11 and the yields of the isolated products was reported, and was presumed to be due to the sensitivity of the electronrich products to decomposition.…”