Organoaluminum compounds are produced commercially and are accessible readily as inexpensive raw materials. Herein, a number of applications of organoaluminum compounds in organic synthesis are reviewed (1982-1985), which includes 1) synthesis of organoaluminum compounds by hydroalumination and carboalumination, 2) aluminum hydrides, 3) alkyl aluminums, 4) alkyl aluminates, 5) hetero-substituted aluminums, 6) Tebbe reagent, 7) catalytic reaction, 8) asymmetric reaction.
Recently, much attention has been centered on the asymmetric reaction by the use of axially chiral biaryls as the chirality-recognizing auxiliaries, and thus, there has been an increasing interest in the construction of the requisite atropisomeric biaryl skeletons. Here we review recent progress in the field of chemistry as follows : 1) Introduction. 2) Prepararation of Axially Chiral Biaryls. 3) Diastereo Differentiating Asymmetric Reactions with Axially Chiral Biaryls. 4) Enantio Differentiating Asymmetric Reactions.
Recent advances in the synthesis of some novel azamodified polycyclic systems have been reviewed emphasizing the synthetic utility of bridgehead imines as well as bridge imines, which have been easily obtained by azide functionalizations of appropriate bi-and tricarbocycles, followed by photolysis, acidolysis, and/or intramolecular aza-Wittig reactions.
Novel carbon-carbon bond forming reactions of carbenes reported in the last several years are selected and reviewed from a synthetic viewpoint. The major part of this article deals with regioselective and efficient C-H insertion reactions selected on the basis of, 1) geometrically controlled intramolecular pathway, 2) chemical modification of substrates, such as substitution by negative charge which activates a neighboring C-H bond, and 3) control of both reactivity and regiochemistry by manipulating metal catalysts. Control of intramolecular 1, 2-H shifts is also described in connection with the C-H insertion. The second part consists of electrophilic reactions of carbenes with carbon nucleophiles as well as with hetero atom functional groups through ylide formation. Other sections deal with cycloaddition reactions such as 1, 4- and homo-1, 4-additions, dipolar cycloadditions, additions to strained sigma bonds, and Skattebøl-type carbene-carbene rearrangements. 1, 2-Additions to double bonds, insertion to O-H, N-H bonds are omitted from discussion.
A new process of multiple sequence of the Diels-Alder reaction, referred to as “diene-transmissive Diels-Alder reaction”, of cross-conjugated trienes, and a stepwise sequence of double Diels-Alder reaction of cross-conjugated triene equivalents are presented. Bis (silyoxy) cross-conjugated trienes, 1 and 2, undergo two sequential Diels-Alder reactions with a variety of dienophiles giving hydronaphthalene rings. Some characteristics of this reaction have been discussed in terms of stereo-, regio-, and chemoselectivity. Next, cross type of diene-transmissive Diels-Alder reaction has been demonstrated by using trienes, 1 and 2. The first cycloaddition stage of cross reaction, which has to be highly selective in the formation of mono-cycloadducts, has been performed by the reaction of active triene 2 with cyclic olefins or both the trienes, 1 and 2, with acyclic olefins. The second cycloadditions with a variety of dienophiles afforded cross type of bis-adducts. In the similar reactions of 2-ethoxy substituted 34 and 1-methyl substituted cross-conjugated triene 36, the initial cycloaddition selectively occurs across mono-substituted diene part in 34 and disubstituted one in 36, respectively. Finally, cross types of stepwise sequential Diels-Alder reactions in a one-pot procedure are presented using the triene equivalents, 33, 35, 55, and 63. Among them, diene-alcohols, 55 and 63, are very useful triene equivalents, as they are readily available from the Grignard reaction of chloroprene. It is particularly noteworthy that the sequential Diels-Alder reaction using 63 provides a new method for the two six-membered rings annelation to cyclic ketones : Naphtho-annelated cycloalkanes with a variety of unsaturation are obtained by choosing the kind of dienophiles, the order of their use, and dehydrogenation.
New heteroatom rearrangements are described : “S, N-, O, N-, and N, N-rearrangements” take place to afford the corresponding 1, 3-thiazines, 1, 3-oxazines, and pyrimidines when 3-alkyl-heteroatom group (MeS or MeSe) -3-heteroatom group (SH, OH, or NHPh) substituted acrylonitriles condense with carboxylic acids in the presence of dehydrating agents such as PPE, PPSE, phosphorus oxychloride, and 1-propanephosphonic acid cyclic anhydride. The key step of this reaction is considered to be the acylation of the cyano group of acrylonitriles followed by the 1, 3-transfer of the alkylheteroatom group. In connection with this study, several new reagents and reactions are developed ; (1) Polyphosphate condensation reagent : PPSE (polyphosphoric acid trimethylsilyl ester); (2) O/S Exchange reagent : 2, 4-bis (phenylthio) - 1, 3-dithia-2, 4-diphosphetane 2, 4-disulfide ; (3) Decarboxyamidation reaction ; (4) Synthesis of S, Se-, S, Se'- and S, S'-dialkyl (di) thioselenocarbonates ; (5) Synthesis of 1, 3-selenazines.